Hello I’m new to the forum and kinda new to Fbodys. I bought a 91 firebird factory 305 car. So I have a 305 n 700r4 trans out my 86 Scottsdale pickup I’m using to put in it. What I’m running into is of course the tail shaft have to be changed due to it being a 4x4 truck but will I have to change input shaft? I bought a another tail housing and it didn’t have the 3 bolts opening for torque arm and I realize that same housing I was trying to use. The input shaft on that donor trans was longer. If anyone can point me in the right direction and give me other options to make things work. Would highly appreciate it. Thanks in advance.

 

Sounds like you're in Scottsdale and need an F-body tailhousing. (Just kidding, but I have one )
The early 700-R4 used a 27 spline torque converter and input shaft setup. These converters interchange with 200-4R and 200-C. As far as I know, these saw use through mid-1984 and even later years, in lighter duty applications; not sure of the cutoff.
Starting with mid 1984 models, they introduced a 30 spline torque converter and input shaft setup. These are common in the V8 third gens. Their converters work for all the 30 spline 700-R4 and 4L60 units through 1992 trucks and 1993 cars. Getting past that, pulse width modulation was used in some 4L60-E units - not interchangeable.

I'm not familiar with any input shaft length changes that would keep a 700-R4 truck V8 trans. from working with an F-body, so long as their spline count matches.