The next step

so mid to low 10's is your final goal? If so that can be done with the above mentioned heads and you'd still be able to run a flat tappet cam which will keep the cost down considerably. Depending on tire size those 4.56 gears might be a little deep. I had an RB in my old car that was incredibly dependable and gave us a best of 9.93. Stock unfilled block, stock rods with MP bolts, stock main caps with ARP studs. Stock crank welded and stroked to 4.15. Light piston set at zero deck and not an overly large port Stage VI heads coupled with an old Ultradyne NF-69 mech cam topped off with a carb shop dominator. Incredibly consistent, and gave us years of good service. It was pretty boring with a shift light set at 5600 and trapping at 6200. Torque!!