i have found that the single chain oil slinger does not fit with a double row chain. that is why the 340 had the hollow bolt to supply oil to the chain.
There is only one oil slinger, it also fits big blocks.
They all had either the hollow bolt, or that hole left open from the factory. You need a hole there to supply oil from the lifter valley to the timing chain.
To the OP:
I would check the crank gear for any differences to the original one. Is the mating surface for the oil slinger flush or recessed or the same compared to the original. If you are installing it correctly, and it's still getting chewed up by the chain, then there is something causing it. I would compare the depth of the new gear to a stock one in the area that mates with the oil slinger.
Then when you find where the difference is, you can figure out if you can shim it or not.
