Mr Gasket 1121G is the PN you are looking for.... 1441 is for some lug nuts LOL For sure I would use those gaskets! Reusing any head gasket is a crap shoot... maybe if it was almost new but not if it is old. You risk a coolant leak, combustion chamber leaks, etc.
When you go to milling the 360 heads, then I'd do more than 318willrun did... I suspect that was limited to avoid milling the intake side and the added cost. A .040" milling limit MIGHT also keep you form changing pushrods but that is a variable you just won't be able to know with .040: milling until it is being put together. I personally would not want to limit myself on performance to try achieve something that may not happen. Milling .040" will put your combustion volume about 2 cc's smaller than the stock 318... which is not much of a decrease, and especially with the prolonged closing of the intake with the cam you have a mentioned. So IMHO look into doing more milling. You drop 1 cc with each .0055-006" of milling. So milling a total of .060" milling would net you another 3-4 cc's of chamber decrease, and folks have gone past that.
With the 3.73 rear gear, you have changed your operating spot in the RPM-torque map so you should be able to do fair. Just don't expect fuel mileage....
