There is a ton of threads making it to confusing to follow for the info I need, so if this has already been covered a million times, I am sorry, and ask for a million and one!

I have an 84 Berlinetta with a 305 4bbl, and 700R4 which has dropped 4th gear and shaky in 3rd. I can't find a replacement that costs less than replacing the car, but have been told that the 2004R or older TH350 will work as well, but I get to many conflicting issues about either that I am lost! So..
1) Will either work in this car?
2) What would I need to swap to either one?
3) Will the tailstock from the 700 swap to either because my Berlinetta has the nasty digital dash setup, which makes the speedo head electronic rather than cable?

I found a post from a mechanic who said the tailstock is interchangable with a 9" tail on the 350, which would fix the issue of mounting the torque bar again.

Any info would be greatly appreciated!