Check both blocks out and use the one with the least wear. Same for the cranks. Looks like you have a Performer and an original 340 intake. Use the best pair of heads, with the valves as close to the chamber and no corrosion. The heads should have induction hardened exhaust seats, so should be good. Plug the holes on the exhaust ports with set screws. Have the intake valves back cut. Run a high pressure oil pump spring and a windage tray. Use a true roller timing chain and a cam from 268 to 260 duration and about .450 lift. If you are buying a new carb, I'd run an AVS2 or a Street Demon around 650 to cfm. If a used carb, then anything from a small TQ, Qjet, 273 AFB or 340 AVS should bolt on and run sweet. Last thing would be an electronic ignition with a quick curve.