The pressure plate and flywheel go together (by vintage), the clutch disc could be anything that fits (splines and diameter).
Bellhousing, fork, throwout bearing = same
starter, flywheel, pressure plate = same
tranny, clutch disc = same
(generally speaking)
T5's were used in more that just Chevies. Muskrats and Jeeps did also.
I'm assuming you are using a 6 volt era starter/flywheel??? if so, I would avoid the 11" clutch setup, the pressure plates are difficult to get and when you do find one, chances are it will rattle (remanufactured). it will work, but it sounds like crap. If you really want an 11" clutch, find one from a 55-62 and convert car over to 12 volts. Remember, the 6 volt and 12 volt flywheels have different teeth counts. You shouldn't have any trouble using a smaller diameter clutch.
FYI, you can use a 6 volt starter on 12 volts no problem, if this is an issue for you. Worst case senario, the teeth are just pressed onto the flywheel, and can be swaped around by the machine shop.
I would advise against the 3:08 for same reasons. It will lug alot more and you will probably need to downshift alot more often. If you go with the 55-64 rearend, you can swap between 3:08 3:36 3:56 3:70 4:11 no problem should you change your mind. As for rebuilding, if the gears are rust pitted significantly, pass on it. Otherwise, bearings can be had from any parts house, and if you take it apart, the Timkin numbers are stamped right on them, so just call up the parts house and give them the numbers. You really shouldn't need to go through all that though, these rearends aren't that hard to come by. Patience.
