I paid $800.00 for a 7/70 std bore 340 motor that was already disassembled. I ended up having the machine shop do the machine work, assemble the short block and set up the heads. With all the other goodies, Rods, Pistons, Valves, Springs, Cam, Fuel Pump, Alternator, Pulleys, and Headers I've got at least $3000.00 in parts(and that doesn't include the 6 pak intake and carbs), another $2300.00 in machine work plus $800.00 for the motor.
The only bonus is the guy didn't know what he had....The heads and valvetrain are T/A heads off a 1970 340 6 pak.
So I would say if you want a 340 be ready for the sticker shock!!