1974 Duster 340 Engine and 727 Transmission Questions!!!

Your 340 has a 69-down water pump and timing cover so that water pump won't work with your 74 radiator.

Look at the front of the damper, there should be a cast counter balance ring on the pulley mounting side that says "Use with 340 Cast Crank Only". If it doesn't have that then hopefully your crank is neutral balanced. Did you get any info from who you bought it from?

Unless you got 340 A-Body mounts with the engine, one of your 318 mount will need modified to work on the 340 block.