Ruger 22/45 upper on MK lower? Grrrrr

Looked back on old threads but couldn't find an answer. I have an old but good Mk I with pencil barrel and want to fit a new 22/45 bull barrel upper c/w bolt that I have. I know the front 'ledge' on the lower needs some fitting or peening to engage the upper's recess but just how much tapping force can I use? It just doesn't want to go in and I HAVE tried more plastic tapping force than seems reasonable. So you Ruger .22 guys ... what's the trick ... brute force ... peen away or what? Next question is the bolt ... the 22/45 is of course different from the MK and lacks the cutout for the manual safety - do I mill out a bolt cutout for the MK manual safety or ??? I know someone will ask why I want to do this instead of just buying another Ruger which is a fair question. For me it's all in the fun of the build and mods and besides being 100% disabled I've got plenty of time on my (bored) hands. Same as when I was an active radio amateur - I didn't buy black boxes because I enjoyed building my own gear. Guess it's like experimenting with handloads when you can buy stuff ready made :banghead:

Thanks Joe. I took your advice and registered there but have to wait for reg to be approved. Can't see why this should be a difficult job since Pac-Lite uppers will fit ANY Ruger MK lower. Ruger says no .. but that's probably because a bit of tweaking is needed in the 'latch' area and they don't want to be sued. Understandable business practice these days but not really encouraging the basic free and adventurous spirit of firearms enthusiasts in the US. Barrett's a better example but not to the likes of the would-be gun grabbers ((