Rear end choices (modified).

I found a guy in NY, elite drive train. A body complete with disc brake kit. Choice of 489,741,742. All rebuilt. My gear choice as well as choice of sure grip type and gear ratio.

I'm considering the 742 with 3.91 and disc type posi, not cone type. Pedestal centers moved in .75 per side.
The 742 has slightly less mass to move than the 489. Keep in mind this is from my limited knowledge on the subject, I reserve the right to change my opinion after I hear what you have to say.

318 KB pistons, ported stock head, .20 shaved off head. Machine block as much as i can without getting into alignment problems with manifold, likely be .030 over on the bore, Edelbrock dual plane Spread bore, 625 Carter/edelbrock, 268 cam, Doug's headers, ceramic. Don't have the exhaust system yet planning on 2.5", wanting to do an aar style but may have clearance issues from subframe connectors.
I'm estimating 280 - 300 to the tires.

But later,,,, I will more than likely put a stroker 360 and be looking for over 500 to the tires. Aren't we all.....