OK, I have ended up with a set of 28 cases and a set of 21 cases. Both are in good shape and I was originally planning to build up a new engine using the 28 cases as I thought they were 21 cases (as that is what they were sold to me as) until I realised the oil pump I have wont work with these cases.

So do the 28 case provide any advantages over the 21 cases that warrent me hunting down a 28 oil pump?