I dont remember the year of the change but I do know the later years where a little larger... I also know you can use the larger one on the early engine without an issue... I just order one from TA with the new screen all ready to go... remember to use a bit of lock tite on the threads of the bolts... I use "the right stuff" sealant on both sides of the gasket as well just to be on the safe side.. You never want a leak on that gasket or it would suck air into the oil.
The '68 was different than the '69-'81 in its shape, and I believe they were 1/2" diameter tubes from '68 to '71. They went to the 5/8" tubes in '72-'81 I think. G
