Yeah, the 10239 is for a external balance, B&M used to make a 904/internal balance, but discontinued it.
A buddy has done this swap in his daughters Demon, showed where I have to cut out the crossmemeber, and he made a template to build a new one, so I will borrow that in the next few weeks to prepare, got the engine bay primered yesterday, hope to paint that, so I can install the motor/trans.
I haven't decided who to order the convertor thru yet.