360 year differences

This should be of help!

Casting Number Engine CID Year Intake Exhaust
2465315 273 1964-65 1.78 1.50
2536178 273 1966 1.78 1.50
2658920 273 1967 1.78 1.50
2843675 273 1968-69 1.78 1.50
2658920 318 1967 1.78 1.50
2658234 318 1967 1.78 1.50
2843675 318 1968-74 1.78 1.50
3769973 318 1975-83 1.78 1.50
4027163 318 1977-86 1.78 1.50
4027593 318 1977-84 1.78 1.50
4323302 318 Fast Burn 1985-86 1.78 1.50
4323345 318 Police 1983-86 1.78 1.50
2531894 340 1968-70 2.02 1.60
3418915 340TA 1970 2.02 1.60
3418915 340 1971-72 1.88 1.60
3671587 340 1973 1.88 1.60
3418915 360 1970-72 1.88 1.60
3671587 360 1973-74 1.88 1.60
3769974 360 1975-76 1.88 1.60
3671587 360 1976 1.88 1.60
4027569 360 1977-86 1.88 1.60

It appears one engine has '73 340 heads and the other has '75-'76 360 heads.