It's always a mess untill you know what to look for:
I'll quote my "standard" answer:
There are three basic production variants of the T-62: Model 1962, 1967 and 1972.
Basic differences are:
1962: Early engine deck (with access hatches and wading rails), early turret (no 12.7mm).
1967: Late engine deck (no access hatches and wading rails but WITH wading hatches), early turret(no 12.7mm).
1972: Late engine deck (no access hatches and wading rails but WITH wading hatches), late turret (with 12.7mm)
Mauro provided photos of the engine decks here:
https://armorama.kitmaker.net/forums/200656#1678818 Cheers,
/E