which trans

Keep i mind that the 200R-4 wasn't made for 425 hp either, and would need upgrades, the engine to trans adapter, a good quality lockup converter, a different length driveline, as well as a completely different linkage setup.
Even a 700R-4 (the big brother to the 200) would need attention before you could run it at that power output.

Would be nice when it was done though.

It would be in the thousands just for the parts.