What kind of gearing were you running? There may also be an issue with the engine itself, being a '70s smog ere engine, it might be down on torque compared to a 235, epsecially one that that been hopped up a bit (hotter cam, milled head).
I have no problem with modern drivelines, I even mad a modern engine suggestion. However, it does bother me when folks say that the original equipment "won't handle modern traffic", which just simply is not the case.
