Here you go.

700r4 to th350 Swap

The legnth difference may vary depending on the TH350 tailshaft legnth you have.

I don't know if it will be an issue for you, but when I revised my plan and decided to use a 518 OD instead of a 727 my 37 Dodge PU I found I have to redo my floor pan due to the increased size of the transmission case.