I have a 1972 El Camino with a de-stroked 400 (377), and a few months ago I had many replacements made to the car, including the starter. On occasion the starter will "grind" when attempting to start (not all the time) and if I wait a few seconds and try it again, it fires fine. It doesnt matter whether if the car is warm or cold, it just seems to happen sparatically. Does anyone have input as to what could be the problem?

Sounds like you may have some bad spots on the ring gear. That or the starter is lame. Pull the lower cover and look at the teeth on the ring gear. If it looks good all around, replace the starter.

Ditto. if the flexplate had a broken or badly chipped tooth and the engine happens to stop on that spot when you shut it off itll do that when you crank it.
how does it sound when you crank it? if its loud or sounds rough the starter may need to be shimmed.

welcome K
x3,,check the flywheel,,if it looks ok,,add a shim or 2,,if that dont do it,, have the starter checked..:texas:

Many starters need to be shimmed. And rebuilts usually have a selection of varied thickness shims with them. They also usually have a little rod, a section of round stock about 1/8" diameter, to check the mesh of the starter teeth to the flex plate teeth. A shim can be inserted between the starter and the block by removing one bolt and loosening the other, 'caus the shims have are slotted on one end.

This is assuming that the gear mesh is the problem........