Do the Moroso pans still have the drain plug on the bottom where it can be hit?
I used a Milodon wide-bottom like the one on Ari's car on my 406" street Duster; had to notch the K about 1" x 1", and for the headers, had to clearance the left rear corner at the bottom (widest part) about 1.5" x 1.5". But I think it's a better pan, becaue it holds more oil lower (away from the crank). I never scraped either the pan or the headers.
I've also had to notch the K on other cars with just a deep sump pan similar to the Moroso.