Nice animals taken with a handgun !
Here's a link to a good article on loading the 45LC in leverguns that you might find helpful.
http://www.leverguns.com/articles/paco/45coltlevergun.htmRegarding your stock, if it were me I'd find a shop that could provide a shotgun butt replacement. Best to check but I believe Win 92 and 94 butt stocks are interchangeable. That was for the originals and don't know about the Miroku versions.
The major issue with Win tube fed levers and a steady diet of heavy loads is just how poorly the mags are attached. A few have reported that mags have come loose on 92's and I've had problems with an 86, which have a similar method of attachment. Even the mag tubes that are screwed can shear the fine threads with heavy loads. On the last rifle I had made up (B71 in 45/90) I had some parts silver soldered in place and used mag retention parts from Marlin. This is working well and nothing has moved.
Regarding the safety, if you intend to keep this rifle I'd look to have the safety removed and rebounding hammer swapped over with Browning parts. It does mean the hole left in the tang would need to be welded and refinished.
Since you are looking at one load and sticking to that you should take a look at the sights made by Ashley Outdoors. They are rugged high viz sights but not so user friendly if you want to tinker with loads and change sight settings often.
HTH
