It all depends on what was done to the heads and shortblock. RA III cores sell for $250-350, and a rebuild for those normally costs $500-700 (more if the shop added hardened exhaust seats, stainless valves, bronze guides, add $350-450). As for the shortblock, most rebuilds get stock cast pistons and rods, decent bearings and cast rings, so I'd put value of that at the core value of the block and crank ($400-600), new pistons, bearings, resized cast rods, cam, lifters, timing chain, pushrods, gasket set ($650-850), machine work ($600-800) and assembly ($600-1200). Of course prices depend on what machine shops charge in your area.
I would put value of a freshly rebuilt, stock-style carb-to-oil pan 68 400 with RA III heads at around $3500-4000. If that same engine had forged pistons, 5140 I-beams, rotating assembly balanced, 2.11/1.77 stainless valves, you could expect to pay $4500-5000.
Geno
