Few years back I had a pair of Carb HP 500's done here locally, cost me right around $7000. Did not need new cams, pistons, etc., just tear down, check over, hone block, surface cut heads, and rebuild with new rings, bearings, gaskets, good valve job, and new Isky SP springs and retainers. So $3500 each give or take a little, I did do the removal and reinstall myself. So update it a couple of years ............. $3700 to $4000 per engine should probably cover it today. Can't really split the upper end only out for you but I'm sure someone will chime in with that.