I don't have the specs on the barrel thread pitch for a Ruger #1. I seem to remember that it has a slightly longer tenon than a 77.
I'm looking at putting a #1 barrel on a 77 receiver.

Both rifles have 1.000" - 16 tpi threads. The No. 1 shank is .840", the M-77 is .700" long. Hope this helps.

Yep! That's what I needed.