Do the TH350 & TH400 have the same gear ratios?

I have a 70 Skylark with a TH350. I will be converting to a 455 with TH400. I have the engine and was still looking for a trans. My question is do all TH350 & TH400 transmissions have the same gear ratios or does that vary by year & model? Waht are the stock ratios for a 70 Skylark TH350 with a 350 2bbl engine? o No:

 

TH350 has a slightly higher 1st and 2nd gear.

2.52-1 1.52-1 1-1

The TH400 is

2.48-1 1.48-1 1-1

You can go to this calculator page and enter the info to get speeds and rpm's..

http://www.1bad69.com/calc.htm

 

Do these ratios hold true for all years and models? Thanks for the info. :TU:

 

Yes