this is the responce I received from Phoenix transmissions about my 250 six cylinder:
If this is indeed a 1965 250 then any or our 3 or 4 speed GM automatics will bolt up to it. You will most likely need to fabricate a crossmember for the rear of the trans, install a flywheel for the automatic, some type of shifter and cooler lines and cooler. In addition, you will have to have a driveshaft made to the new length and yoke. If you are happy
with the rpm of your top gear then the PT350HD will work well, or if you want lower rpms look at the PT700R4HD. Let me know if we can help.
