The forged crank pulleys will not work on a cast crank balancer, you need to find a pulley set from a cast crank! The difficult part is going to be finding them from an A/C car, as those are different from non A/C cars as well!!
This is news to me, as I have allways swapped pulleys from year to year off cast crank 318s, right onto steel crank 340s.... Maybe that 73 340 balance weight is in the way of the pulley? never thought of that....