Old 15x6 Cragars, Tire Size?

So I'm going to get tires, hopefully tomorrow, on four 15x6 old school Cragars.
$40 off coupon expires soon!

Trying to figure the best size to get, and whether or not to get small and big, front and rear.

Leaning towards same size all around.

62 Dart, terrible pic below. It came with 215/70R15 all around on cop wheels, which I think are 15x7.

Cragar ad states 7.00 or larger tires, which I guess means width.

I like how the 215/70s fill out the wheel wells, although I wouldn't have thought it would, but just my ignorance.

Called a few tire places, one guy seemed to know his cars and tires, looked up a few sizes and was leaning towards 225 or 215 70s.

Is 225/70R15 too big for a 6" wheel?

Anyone recommend another size?
Or big and small on the same size wheel?

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