When doing this swap keep in mind that the 727 is longer then the 904, so either the driveshaft will have to be shortened or if available one from a donor M-body with the 727 and same rear will have to be used. The driveshaft yoke of the 727 is larger then that of the 904, so it too will have to come from a 727 vehicle (MP also sells this item new). Another item that isn't compatible between the 904 and 727 is the torque converter. Whether you use the torque converter that comes with the transmission, or buy it seperately, make sure that if you have a 360 it has the 360 weight (or if the converter has the weight but you have a 318 don't forget to remove it), and that you're not using a non lock-up converter with a lock-up transmission or vice-versa. Lastly the pivot bracket that bolts to the transmission for the linkages is different between the two models. If the transmission doesn't have one you'll need to get one. This may also be the time to part with the 7 1/4 rear end if one is still driving the rear wheels. They're the weakest link in the drivetrain and if you feel at all that you'd be eventually moving up to the bigger rear it's cheaper to shorten the driveshaft just once, then a 2nd time down the road (the bigger rear is roughly an inch longer then the 7.25).

To do this swap you'll need a big floor jack, 4 safety stands, socket set (universal sockets & adaptor, and extensions are a necessity), breaker bar with 1 1/4" socket and short extension, wrenches, screwdriver, needlenose pliers and a drainpan.

REMOVAL
-Both ends of the car must be on safety stands. Remove the driveshaft.
-If the dustcover is not inplace remove any flexplate-to-converter bolts that you can, then turn the engine over in short bursts until you can get the others out. There will be 4 bolts in total. Disconnect the battery and remove the starter. Using chalk or paint mark the last tab of the flexplate and that spot on the torque converter.
-If the dustcover is inplace disconnect battery and remove the starter. Remove the dustcover bolts aswell as the 2 support bracket bolts and remove the cover. Remove the flexplate-to-converter bolts that you can get to and then using the breaker bar and 1 1/4" socket turn the engine clockwise until you can get to the rest.
-Back off the parking brake adjusting nut enough to remove cable from the 2 hooks at the crossmember and also remove the hooks. When doing this notice the notch that each hook holds into.
-Remove the brace that holds the exhaust pipe from the transmission.
-Disconnect the 2 cooler lines from the transmission, remove the speedometer pinion gear, unplug the neutral safety switch and disconnect the linkages.
-Place jack lengthwise under transmission with pad under the transmissions pan. Remove the nuts for the crossmember retaining bolts and slightly raise/lower the jack as needed to remove the 2 bolts.
-Start removing the bolts that hold the transmission to the engine, raise or lower the transmission as needed to gain access to the ones higher up. The hardest bolts will be the two at the top of the bellhousing, to get to them lower the transmission as far as possible with the weight still on the jack, and use extensions with a universal socket. You should be able to see or feel the bolt heads enough to get the socket on them and remove them.
-Once all the bolts are out take one last look to make sure everything has been disconnected and carefully wiggle the transmission while pulling it back to disloge it from the engine. Once this is done slowly start lowering the jack keeping a close eye on everything to make sure nothing has gotten caught on thr tranny or is still connected. The dipstick tubue might have to be removed. When the jack is as low as it can go slide the transmission onto a board, creeper, or skateboard and slide it out from under the car. At this point if you won't be doing anything for a few days and would prefer the car be off the stands it can be lowered, making sure that the wheels are blocked so it can't roll away (you now have no parking brake and no transmission to keep it still).

Once you've gotten to this point compare the two transmissions side-by-side and look them over to see if anything has to be switched over. Unless they are identical the crossmember will have to be, and if the new transmission doesn't have the studded nuts inplace that the exhaust brace bolts to switch them over one at a time. You may notice a few other things aswell. Look at the two torque conveters carefully and mark the same spot on it that was marked for the flexplate on the old one. If a 2nd flexplate is handy this might help find the spot.

INSTALLATION
Installation is basically the opposite as removal until you get to the final details.
Once the new transmission is on the jack make sure the torque converter is fully engaged to the pump. The hardest part of putting the transmission in is lining it up with the 2 dowels on the engine. Once you have it lined up put a bolt in each side to keep it there and start putting the remaining bolts in. Then go around those bolts a second time and make sure they are tight. Raise the jack as high as you can to get the crossmember bolts back in and secured with their nuts. The jack can now come out and you can start reconnecthing the safety switch, parking brake cable and cooler lines, when it comes time to do the linkages remember to use your new pivot bracket. Get the mark on the torque converter lined up with the mark on the flexplate and loosely install the bolts you have access to. Use the breaker bar to turn the engine clockwise until you can get the rest of the bolts in and then go over all 4 a second time tightening them down. If you managed to find a driveshaft already the right length put it in, if not you'll have to put the 727 yoke on the old one, and have it shortened to fit. Drain the fluid, change the filter and fill it with fresh fluid. Adjust the kick-down and you're done. You might also want to adjust the transmission bands.

At this point the swap should be done and you can continue drivng your car once again!

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