Hi. The only 410 references I've been able to find are for '66-'67 Mercury. The 390 as such was supposed to end in about 1976 for the pickups, so that's the most likely thing.

The 410 is a 390 bore (4.05), with a 428 crankshaft, giving it the longer stroke and more displacement. The cranks will usually have 1U or 1UA on one of the counterweights.

Hopefully DennyW will jump in here - he's very knowledgeable on the 410 engines and can straighten out my errors.