Some of the RPM castings OOTB are as poor as mid 260s. IIRC, modern can get 320ish out of em CNC'ed. That would make a monster difference on a 500 incher.
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
