The reason I wanted to leave a follow-up, is that I was astonished by how little info was available online- and how unresponsive various Ruger forums were. Considering the widespread following for the No.1 rifles, one would think that even though the No.3 rifles were a less-produced step-child, that info would flow like the spring flood. Not the case to say the least.
Considering the eventual truth that any 1/16 roll pin would do the job, it is inconceivable that Ruger afficiandos wouldn't know that this would be the case. In any event, I got more help, more quickly, on here and from a small mom and pop gun supply place than from Ruger or anyone they recommended...or from Ruger forums. So, if posting it here helps anybody down the road, I feel good about that.
I love the rifle. A nice, quality falling block at a price that didn't require selling a child.....in a caliber I already had investment in....win-win!