They are NF bolts. I was mostly able to re-use most of mine. The funny lock washers are sometimes a problem. I try to clean them first, before I try to remove them. I know, sometimes, that is not possible. I use never sieze, when they go back!
The military had a re build kit. Try the vendors that deal in M37 stuff. It had everything. I want to modify the main jet with a little smaller hole in it. It still runs too rich on our present day gasoline. The engine is getting broken in now - about 800 miles on it- all new stuff - .040 on the pistons, and lots of machine work. Maybe a mixture that has a lot of ethonal in it would be better. I have a therory: Our modern day gas takes more air to burn it clean, then the stuff they were making 50 years ago.
Lee in Alaska