On my Ford the bolt holes will only line up in one position

its a 460. i guess what i need to know is if the weight on the flexplate is to make just the flexplate balanced or does it co-balance with the crank and harmonic balancer.

I was told to bring my flex plate to the machine shop when I had the engine internally balanced...  I'll check to see if I can see a counterweight or any sign of balancing done to it tommrrow.

You may need shims for your starter

Guys, you CAN NOT, MUST NOT indescriminantly swap counterbalanced flywheels/flexplates/harmonic balancers for non-counterweighted versions!!!!!!!!!!!

The counterweights you see on them are there to compensate for changes the manufacturers made inside the engines. "Internally balanced" engines will not have the counterweights, "externally balanced" engines will have them.

With the BBC, all FACTORY engines 454 and larger REQUIRE the counterweighted components. 427 and smaller were internally balanced from the factory and thus require non-conterweighted components.

With the 460 Ford, the early engines used non-counterweighted components. A change in the internal block design, where they extended the cylinder bores down closer to the crankshaft, forced a change in crankshaft design. This change made the counterweighted balancer and flywheel/flexplate necessary.

Any "externally balanced" engine can be converted to internal balance, but it must be done by an engine balancing shop. They will need to add "Mallory Metal", which is heavier than the metal of the crankshaft, to accomplish this. It is NOT done by simply swapping parts.