Heads have been port matched to match my Champion CNC ported intake manifold at the openings of the intake tract.
I understand that there is Not enough meat in the Port tracts in iron heads to open them up fully to the 1200’s
I was considering 1200's and the pan recently. I bought them plus a OE pan style. After comparing them, I realized the Pan gasket fit much more to my liking and there wouldn't be a benefit to the 1200's. I have Champion Irons.
If you do go with the valleypan, the guy who makes them has them cheaper on his website / calling him. There wasnt much sense in me doing like other said if you dont have port matched heads and or intake. the 1200s would work great for that, but i went with the thicker paper style 1pc gasket. You can also buy the metal version of that, which doesnt have provisions for the EGR stuff.
the 1pc gasket fits easier because it "clips in", so you dont have to fumble around placing it, and it moving under torquing. even if you tack it up it will still move slightly.
Paper gasket w/valley Metal gasket w/valley