Finding a lot of th350s for sale really cheap...I heard these will bolt in without any issues and are more durable than the 4L60E, my question is what do I need to do this conversion in a 4th gen fbody? I assume a custom drive shaft, kick down cables maybe to?

its alot more work then that. need a special crossmember with the torque arm mount. the wiring harness will have to be modified to accept the new tranny IF it has lock up. as well as a speed input. otherwise the tune will be radically off. as well as a custom tune to remove all the 4L60E parameters. a 4L60E can be had for 400 bux if you search around. the 350 route is not worth it unless your racing.

Th350 or 400 is easy if ypu get a manual valve body and have ypur computer retuned to a 6 speed computer. However if your looking for the cheapest way that isn't a cheap option. A used stocker is the cheapest option.

also need a different driveshaft

ah thank you