th400 to 700r4 transmission swap in 1980 c10 frame

[56hotrodred]

So all this talk of rear transmission crossmember in my 1980 frame has got me thinking about my upcoming transmission swap.

The 1980 frame with 1956 body and my mock up used a side mounted 283/350 and th400 transmission.

My transmission guy is recommending 700r4 which he will rebuild and upgrade to put behind a gm ramjet 350. So far I am agreeing with him on this choice!

First question is can I use my stock th400 transmission mount with the 700r4 and simply relocate it as the length is different?

I like the look of the stock transmission mount as it bolts on one side of the frame. This might assist in reducing frame flex! This is opposed to using an aftermarket crossmember that simply bolts to bottom flange of frame!

Second any difference in physical size of transmissions? Will it fit under cab?

Any other thoughts on my transmission swap plans that I should be thinking about?