Question: Can I use the same computer, sensors and card from my original 305H.O.?
Answer: Yes, in fact I recommend it. This will allow you to stay legal. You can also use the same exhaust manifolds, intake manifold and accesories. The exterior dimentions of the block are the same.
Question: What about the stock intake manifold?
Answer: The stock intake is a dual-plane aluminum manifold and works pretty well. If you are using a center-bolt heads you will need an intake manifold that's made for these or else be prepared to do some drilling and modification. There are upgarades availible but IMO there other upgarades that need to be done first.
Question: Does the computer or the carb need to be adjusted for the extra cubic inches?
Answer: It doesn't have to be but it helps to use different secondary metering rods in the carb. Some people have recommended using rods from a late 70's Caprice. In some people's opinion is that you don't have to make any changes to the computer, but there are different opinions about this.
Question: Will my TH200-4R trans. work with a larger engine?
Answer: Yes it will bolt-up no problem. The extra h.p. may shorten its life a little bit but with a proper rebuild it will be just fine. You could also upgrade to a 700-R4 trans. but this involves modifying the cross member, shortening the drive shaft, and fiddling with the shift linkage and kick-down cable.
Question: What about the knock sensor and other electronic sensors?
Answer: The knock sensor threads into one of the drain holes at the bottom of the block so that's no problem. The 305H.O. (L69) block has a threaded hole just above the oil filter for the oil pressure sender. Other blocks might not have this hole. You can either drill and tap a hole here or else tee into the oil-pressure switch that's under the distributor. There's a water temperature switch that goes inot one of the heads but most heads usually have a provision for this. There are some other sensors in the intake but if you are using the stock intake then this will not be a problem.