WANTED 1968-70 340 Exhaust Manifolds

Pleading ignorance here....

But whats the difference between 68-70 and 71-73??? Are the ports smaller or something? Also, why are gaskets so $$$$

I just paid 30$ for a set of manifolds off a 73 340 duster...I'm going to put the on a 360 in a '67 barracuda.


Thanks Jim