What stall speed do I need

Still better to have one specifically built for your car and how you intend to drive it, IMO.

It's just too easy to have one built anymore rather than buying an off the shelf converter. Remember it's the critical link between your engine and the rear, and the performance of the entire package.

I've sent my info to 3 places now and waiting to hear back from them.
What is a fair price for a custom converter ?
I did see a price from one place online of $608, but I don't know if that is a set price for whatever I want or just a basic converter price they had advertised.