The blocks come installed from the factory. You can use an objective up to 44mm with the medium rings. If you go with a larger objective you can send the medium rings back to Ruger and they will send you a High ring to replace them with.

I have seen several #1's that were good shooters out of the box and a few that weren't. If you buy the rifle and it isn't a good shooter you can have the forearm hanger bedded and this will float the barrel away from the forearm. This usually takes care of any accuracy problems. Bedding the forearm is not much different than bedding the action on a bolt gun and shouldn't cost much more. I think the #1 is one of the finest factory rifles produced.