I don't see why you couldn't just put an exhaust and intake manifold off of a NA 617 engine in place of the turbo manifolds. I'm skeptical of your mechanics claims that the 617 turbo will eat a 5 speed tranny. Like I said earlier several members of this board are using a 4 speed mated to the turbo engine with no issues. The 5 speed is quite rare in this country, so there are not as many people using it with the turbo engine, but I do not see why it would be any different than the 4 speed.

Where are you located?

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine