Here is the complete guide to installing an MSD 6A, 6T, 6AL, SCI, SCI-L high performance ignition system. I cannot however, give you details on mounting options, as there are just too many possibilites. I used both the battery relocation (and positioning the MSD in its place) and the "squeeze into the engine bay" methods. It depends on how creative you are. With that in mind, lets review the parts you need.
Disconnect battery.
Hopefully you are familiar with the basic Tercel ignition system. Distributor, rotor, etc. The distributor has two wires coming out of its base. Depending on the exact year, one wire may be black/red or black/orange. The other is black. Remove distributor cap and rotor. Remove the dust shield. The two wires will terminate at the stock ignition coil. Unbolt the wires from the coil and pull wires away from distributor entirely. You might want to cut wires at the base of the rubber grommet so you reuse the grommet.
Now unpackage the MSD components. Depending on where you decide to mount the units will determine how much more wire you will need to run. But, lets assume you picked the perfect mounting location. The MSD CDI has several wires. The heavy black and heavy red are naturally, for power. Then there are a set of white/red and orange/black wires. Do not use the purple/green wires. The white/red wires get the distributor signal, so they attach to the stock black and black/orange wires you had taken from the distributor. MSD RED ATTACHES TO BLACK/ORANGE. MSD WHITE ATTACHES TO BLACK. Note, the TACH ADAPTOR has both RED and WHITE wires which must be spliced in accordingly at this stage. Your tercel will not run w/o the adaptor. The Orange and Black wires are for the coil. If you have the blaster SS, connect the MSD ORANGE TO THE POSITIVE TERMINAL. MSD BLACK TO NEGATIVE TERMINAL. Then connect MSD HEAVY POWER Wires to the Pos and Neg (or chassis) of the battery. Hook up the MSD noice supressor inline with the heavy power cables at this step. THE CLOSER YOU CAN MOUNT THE SUPRESSOR TO THE MSD CDI, THE BETTER. This part is now finished.
Next comes the "assemble" stage. Drill into the new distributor cap with at least an 8-32" bit at the stock coil location (right where the coil would normally sit). You are going to convert the internal coil cap to an external cap with MSD power tip. Since the bolt provided is not long enough, you can a) buy an 8-32x3" bolt and cut it w/ a dremel, or b) cut the plastic power tip. You just need the bolt fit. Since the Stock coil IS NOT ACTIVE, you must BEND the METAL TAB inward. DO NOT REMOVE THE STOCK COIL. Seal it as best you can with silicone or tape to keep the tab from touching the modified cap. *Note, at this point you may want to smear the terminal tips inside the cap with a little dielectric grease to extend the life of the cap." And this part is now done.
Follow the direction that came w/ the wire set to cut to the correct lengths. Also cut the the provided external coil wire to the correct length. This step is now done.
So heres what you just did. You took the stock ignition wires (BLACK and BLACK/ORANGE) and connected them to the WHITE and RED wires of the MSD CDI, which will amplify the signal by the ORANGE AND BLACK wires to the BLASTER COIL. The coil receives the signal and boosts up 48,000 volts through external coil wire to the distributor cap. From there it goes the way of normal combustion. Reconnect the battery wires and fire up your tercel.
NOTE* I have used two wells caps trying the MSD with a BLASTER SS coil. Since the MSD uses multiple sparks, and the BLASTER triples stock sparking power, the distributor caps will wear out approximately 6x-10x faster. I got about six months or 3000mi of perfect performance, but afterwhich, the cap needed replacement. I heard that Beck/Arnley or Autolite are better quality units, available at Pepboys for nearly the same price. I cannot vouch for these companies though as I use the MSD setup w/ the stock coil. Regardless of the cap you used, if you smeared the terminal tips with that dielectric grease you won't have to replace it as often. Instead, file down the tips and clean them off a bit. Then reapply some more grease. Oh, and naturally, all modifications are at your own risk.