Why are you swapping out the timing cover and damper?
The 1-piece rear main seal SBC engines use an externally balanced flexplate/flywheel, but the damper
is neutral balanced. So you want a neutral balanced damper if the engine is going to use the stock crankshaft.
If you use an early damper you can't use the reluctor ring (if your engine used one) on the crank snout along w/the older type (longer) damper snout, else the pulleys wouldn't align (bottom would be out 1/4" too far). You do not need the reluctor unless you were using the factory EFI. A thread comparing the dampers, etc. is here
Info on the differences between the plastic and metal timing covers is at post #6
Info on the various SBC timing tabs and damper lines used prior to the Vortec/plastic timing cover is here