Blasphemy, of course, but I can certainly see the point. The only Mopar option is to use a 727 with a Gear Vendors OD or a 518 with an adapter and the OD unit on them is weak. But if you were to go with a 5.7 Hemi you could use one of the 8 speed truck automatics which are better than any of the GM offerings.

Back to the question...cut as much as you need to cut and as long as you are at it ditch the torsion bars for a modern suspension...there that ought to stir the wrath of the righteous faithful.