So I put a stronger 350 in my El Camino, and now when I partially accelerate my whole car shakes. Of course when I stomp on the pedal it kicks down and goes vroom vroom, but what is the deal with all the vibrations during a partial acceleration? Also, I'm looking at having my transmission rebuilt. What kind of torque converter would be good for someone wants to be running with no more than 500 hp. I'm lost as far as where to go from here...I got my engine...now what?

If a tranny shop installed the transmission, take it back and complain. If you installed it, take it to a good tranny shop for diagnosis and an estimate to get it repaired. You can take it or leave it at that point.

It shouldn't vibrate and that will tear up something quickly!

Just guessing it could be the Flywheel out of balance or broken or missing bolts. Then it could also be something going south in the torque converter.

As far as a Stall speed for a converter. No one on this board, not knowing your specific CAM and other particulars can tell you what stall speed to get and be correct. It is possible that someone could get lucky but its probably not going to be the best one for your application.

Call TCI and talk to them about a Stall converter! Man they know their stuff and will get the best one matched for just your application. If you have dyno results from your engine or a simulator you could probably get close to the right one. Maybe it will stall correctly and maybe it wont.

If you going to spend the cash make the effort to get the right thing.