13's, stock '71 318 short block.

I think if it was me, knowing that these are really place holders but possibly could be tweaked to feed a better engine easily... I'd look into RHS LA-Xs with the 1.92 intake. I know Hughes has them for $875/pr but you'll need to upgrade the springs. My reasoning would be the EQs or stock Magnums would not be enough in any form to feed a decent engine nor will they accept larger cams later. So I think overall those heads might be "the best fit", knwoing there will be changes relatively soon after I'd get the heads with more potential from the get-go. For a camshaft... You almost need to look at "claimer" type cams because you can't do too much lift with no valve relief. So I'd try to spend the coin on a set of rockers and run a solid lifter cam in it. Also, the heads are decent enough that you don't need the dual patern cam. Something like the Magnum 270S would be great in it. Keep the intake dual plane (Performer 340/360, Crosswind maybe?) and carb under 650cfm and I think a basic 4150 series DP would be fine. I'd also run a convertor in the 3K range. I think if the lower end is ok that combo should get you close to mid 13s in bad heat, low 13s after it's all debugged in good air.