I was going to have mine d&t'd at a local gunsmith but they charge $40 per hole so I ended up sending my two Gov. Target barrels along with a 5.5 bull to Ruger and had them do it. $65 each and $30 to ship them in one box, I only shipped the barrels, no frames. https://ruger.com/service/partsService.html
Had them back in about 10 days and they did a great job and even mounted the new version scope mounts on them. I swapped those out for Tandemcross mounts which I prefer. https://www.midwayusa.com/product/1019657990
As to the Sun-optics mount, it is a copy of the discontinued B-Square mount. I have two of those, one on a 5.5 bull and the other on my 5.25 heavy taper. You need to be careful mounting them as they fit very tight and can scratch the finish on the gun but if you remove all the mounting bolts and clean everything first, they slide right on and bolt up very solidly. You can also use the factory sights with the mount in place as there is a channel below the rail allowing for that. There is also a B-Square mount which is single point and is also very solid but doesn't allow for removal of the optic once mounted, however, the factory sights remain usable. Both are on Ebay now.
https://www.ebay.com/itm/B-Square-Ruger-Slide-Aimpoint-Mount-Mark-I-Mark-II/133525571557
https://www.ebay.com/itm/Vintage-B-Square-Scope-Mount-Ruger-Mark-1-22lr-semi-auto-pistol/274512557820
I would recommend d&t by Ruger as that keeps the optic lower on the barrel and shouldn't have any affect on the value, in fact, is might increase it since it's done by the factory.