Initially NO 1 action rebarreled to 22-250 w/ 7 twist and 26" stainless barrel set up with sight blocks to use Unertl scope. Gives excellent accuracy w/ 69,77,80 and 90gr bullets.
Primary load will be the 80's but even though the twist for the 90's should be a bit faster, not bad at all. Second barrel is 348Win of same profile, but 23" long and chrome moly. This barrel installed Ruger rib, issue flip rear sight, NECG hooded front sight. Use Leupold Ultra Lite 2.5x for scope. Just yesterday got around to the first firing of the 348 and can say pleased with the performance.
Caliber is not known for match accuracy, but using Win. SilverTip factory loads you can keep 5 shots under 2" at 100yds. using bench/bag. I was able to secure large lot of brass and factory loads some year or so ago and good thing for 348Win. not common and new ammo is expensive compared to others. The process of switching barrels is not a big deal as long as you use the same action for changing of the extractor is all you really have to do. Will say my first attempts at taking the NO.1 apart was a struggle, but watching the video from the Ruger site, helped a great deal and now can do it easily. End result, 600yd.+ targets/varmints in the summer, bigger critters in the winter.
Also have a NO.3 built in 45/70Gov't and giving some thought to another caliber for that one. The 45/70 barrel quite a bit heavier and couple inches longer than original factory 45/70 for that thing was a killer in recoil with short skinny barrel. Most likely will end up with 223 since I have large supply of components. As long as you use the same action only limitation is your imagination for these Rugers.

Have you ever tried the swap without changing the ejector? Reason I ask is thay I have rebarrelled/rechambered quite a few, and never changed the ejector. Ruger sells different ones for different calibers, and years ago I bought one of all the standard sizes to keep on hand. I found that, when swapping a new one, it never fit the new action and required lot of fitting and that I have to keep them in separate envelopes since most are so close I can't tell them apart. The Ruger design is inherently self correctng to a point. Given the large difference in the case heads, they might not be reliable, but I have seen them work over quite a range. Swapping the ejector is not hard, once you get the knack of lining up and inserting the links and breechblock, but i is sort of twiddly, and I wouldn't do it as a practice simply for the potential to damage the finish and metalwork on the action when removing and installing the lever crew assembly. You also have to use some sort of barrel and action wrenche, I presume. I shudder every time I have to do that to a finished gun. It's one thing to do it to a working benchrest gun, another to do it to a nice rifle.

Reason I just buy caliber specific ejector is they aren't expensive, but you are right often times the std. ejector works OK. I do have access to shop with barrel wrench/proper action holding device, etc. and 'smith and I are careful to not marr finish. No problems so far.
Both of my current NO.1/3's are fairly easy to remove breech block, linkage, etc., but they are closely machined and you have to hold your head just right for them to drop in, but done it so many times now, not a problem. It takes us about 30min. to do the switch and that's with discussing all the world's problems. As you are aware, that firing pin seated in the breech block is a bit of a trick to install, and did not intend to take out first time, but figured out how to reinstall. Ruger's video does not cover that item. Did require some strong lanquage, but it gave up and went in just fine. Should mention that going from say 22Hornet to 45/70 requires some slight modifications to the rearward portion of the breech block, same true for the 348Win. because the rim diameter is actually larger than the 45/70 since parent round was the 50-110. The "valley" in the breech block near the rear needed just bit of metal removal(fine grit drum w/ Dremel) solved the issue and did not bother the integrity of the block itself. As I am sure you are aware, this barrel switch process is fine as long as you are using the same action the barrel was fitted in the beginning for variance in another action would most likely not fit up correctly in terms of headspace or timing if you will. As most of us, have all manner of rifles, but find the Ruger NO 1/3 to be one fine firearm and other than some huge caliber(600Nitro,etc.) could rebarrel to take about anything you could imagine.