Getting Transmission Rebuilt

As much as I would like to rebuild it myself, I decided to take the Scamp in to get the transmission rebuilt next week. It has the 904 with the 318.

Is there anything specific to ask or watch out for? Specific shift kits and maybe a new stall converter? I know it should match the cam but I might not get the motor rebuilt for a while. So is it better to stick with the stock one for now or put a new one in with stock specs? They mentioned maybe a mild one that is 2200.

I asked them about putting a new rear main seal on the engine. They asked what type I had but I wasn't sure. They said there was one kind that wasn't the best and if it was that they couldn't guarantee the seal.

Thanks for all the input