I wont say theres no such thing as a cast crank-pulley for a 340 or 360. But if you ever found a cast pulley to fit on 340/360 or any auto engine,for that matter, you better not rev it past idle.
But if you mean that you put a cast-crank pulley, which would be a steel pulley,from a 360 with a cast crank,onto your 340. Well thats ok then.No problem.
Now, about steel small block mopar crank pulleys? They will all interchange. Some require minor filing off an offset hole. None of them will require balancing.
If you have a vibration, and the pulleys are not wobbling,they are not the source. Now a fan? That thing can cause a vibration, along with anything else attached to the crankshaft. But then, you probably already knew that.
Are you aware that there are 2 types of 340 balancers as well? And that the balance required for 360s is different than that of the 340s?The balancers will all physically interchange.But each type of crank assembly requires its own balancer.
As to stock LAs
All stock 360s are a cast crank motor and require a 360 balancer only.
All early 340s were steel crank/internally balanced motors, and use the early, zero balance, balancers
All late 340s were cast crank motors, and used a late-340, external balance,balancer.
The change over year for the 340s was IIRC 1972or 73.I think 72s were steel, and 73s were cast.
All stock 318s are internally balanced and any 318 balancer can be used on any 318. Or on a steel-crank 340, for that matter.
Each grouping needs to be considered as a set.
If your 340 does not have stock parts, or factory stock-replacement parts, in it, it may require different than stock balancing.
PS the 360s also use an offset-balanced convertor.AFAIK, of the sbm, its the only one that does.
