Fair price for a '70 340 engine that needs rebuild

Heads in the condition you state are worth $1000. The short block is worth more apart then together if everything is OK and standard. Another $1000 apart and inspect-able. If it is together "as is" its worth $500. You never know whats your getting when you can't see whats inside. Many times guys do not use the rods and pistons Due to the cost of resizing the rods and new bolts its cheaper to get new. But the hardware for the block is very desirable . Timing cover ,windage tray, Pan, Oil Pick up, 340 valve covers are on their own, slinger, dip stick. And all the things such as bolts and reusable that add up pretty quick.