Transmission

So here is the TH350 transmission I got, with a new coat of paint, all ready to go (soon as my new flexplate comes in).  FYI, there are 153 tooth and 168 tooth flexplates (flywheels), and which one you get depends on the torque converter you have.  In my case below, if you measure from the center of the torque converter to the single larger bolt holes, I get 5-3/8", double that gives me 10-3/4" circle.

There is a good article that explains it here.  Just make sure you get the correct starter that matches up to the correct amount of teeth that you flexplate has as well as which bolt pattern you need on the starter.