There are actually three “sizes” of TH350 – short (6”), medium (9”) and long (12”) tail shaft. The key measurement is the overall length, i.e., from the lip of the bell housing (where it bolts to the engine) to the lip of the tail shaft. The short TH350 measures; 27-11/16”, medium is 30-11/16 and the long is 33-27/32”.

700R4 in all but Corvette applications measure 30-3/4” The Corvette is (for some strange design/engineering reason) 29-7/8”.

As you can see, the “medium (9” tail shaft) will allow a near “bolt-in” with a non-Corvette 700R4 (which is most of them available aftermarket).

The TH350, 200R, 700R and 4L60 all use a 27 spline yoke.

Not a real difficult swap – but I’d recommend a visit to the boys at “Bowtie Overdrive” as this is all they do and they do it very well: Bowtie Overdrives

Let us know what you decide!
Glenn