Suggestions for my Dart
Man I can't believe such a beautiful A body is just across the "Ashley" from me :). From my 70's/80's back round, you've nailed it! That car has got to be already "street fast" against 90% of N/A cars running the roads around here these days.
Moving forward, and since you have them, the Eddy heads would be a reasonable upgrade. I personally would have them gone over.....Valve job, mild port & bowl cleanup, and also confirm the valve guide clearance is acceptable. If you're going there, you want to get the most out of them. Besides that, if the roller is truly in your budget/future, I'd have the pushrod holes opened up for clearance? It tends to be tight with the "tall" lifters.
As far as the O/D.....With your current tires and a 3.55, unless you're running the Mark Clark, I26, or I95 on a regular basis, I just can't see spending that coin from a cost/benefit basis. With the 3.91's, maybe, but for weekend/hotrod use, I'm still not totally convinced on that yet?
Back to the roller cam replacement, a high lift, moderate duration grind would probably work best with the mild gear and/or O/D. I'd look for something in the .520/530" lift range with 230/235* @ .050 to start with? All the final details will need to be determined before any specific grind could be recommended, and a custom ground stick may end up being your best bet?
Sorry for being so long winded.....But I will sleep better tonight knowing there's a super nice Dart here in the Low Country. :)