Is it really a transmission problem?
I'm wondering about his first post - he says the engine won't rev over 4K, and is redlined at 6K - could this actually be a rev limiter problem that's related to getting a different distributor signal? (I don't know anything about either engine, but rev limiters can cause significant jerking, and he hasn't said anything about a SHIFTING problem, just a REV problem that can occur in any gear! If, for instance, the 300E is a six and the 190 is a 4, that would make the rev limiter (assuming it has one, and most EFI systems do) operate at 2/3 the rpm on the 300E that it would have on the 190... (I'm making a lot of assumptions here, one being that the engine management system, or at least the rev limiter is still for the 190)
Just a totally uninformed, uneducated thought....
1982 300D/4.3 V6