Brad,
Just purchased a Canton pan and windage tray for my FE. The studs are 5/16-18 x 1 1/4" set screws. The nuts are flange type.
I just purchased a similar setup for my valve covers. I obtained them from McMaster-Carr
http://www.mcmaster.com
They also have studs, similar to carburetor studs with a positive stop on them, but considerably more money than the setscrews. Plus that style stud is coarse thread on one side and fine thread on the other. Mr. Gasket, Milodon and Moroso also make a similar "carb stud" but they were steel/
zinc plate. I chose to go with stainless. McMaster offers all types of materials.
I looked at the ARP ones. They are great, rounded tips for quick, no cross thread starting but they are pricey.
You only need the four corners to make it work, you could use bolts for the balance, once you get the pan and tray installed.
Regarding the different thread depths, I used some small pieces of music wire cut off and put under the stud to space it out. That way, when I ran it down, it bottomed out on the insert and the exposed portion was similar for all studs. Looks better. Also used Loctite to place the stud. Prefer the nut come off rather than the stud come out
I use a quick-start stud on the valvecovers of a dragster since we have the cover off after every run. I don't see you removing the pan that often so don't feel the quick-start type would offer any benefit, other than to the suppliers.
See you on the Hurricane board.
Paul
ps: add my compliments on your avatar (or better yet, TO the one who posed for your avatar)