The B-50 wasn't that similar to the B-29. It had a much taller vertical stab, different
engines and nacelles, and different nose glass for the bombardier's station. I believe
the armament was different, too but, I'm not totally sure of that.
I think MINICRAFT made some B-50 versions but, again, I could be wrong.
Good luck on your hunt
Ray
Make that ACADEMY...They have the RB-50G in 1/72nd