Posted on the rimfire board as well:

I have my father’s 99M1 that I learned to shoot with as a child. Several years ago he was riding with the gun on his 4 wheeler and broke the stock when he flipped the 4 wheeler. He took the gun apart to clean it and never put it back together. When he died a few years ago, I ended up with a box of gun parts and pieces. I know everything is not there but most of it is. I can find a stock but what I need is someone who is trustworthy that can put this gun back together. It probably means more to me than any other gun I own. Any help would be appreciated.

It's the same as a model 60 it should not be hard to put back together yourself. Go to rimfire central and ask questions.

A copy of the old NRA gunsmithing manuals or JB Woods firearm assembly books might help and be as close as your local library. Rimfire Central site might also be a good online resource.

I have never taken one apart but being a medium priced gun it is probably a simple design.

Also look at the Marlin Model 90 take down/maintenance information. It is very similar to your Marlin and the Model 90 is still being made. Some parts might interchange.

You might want to buy a neoprene recoil buffer to replace the OEM part when you rebuild.

You'll want to date your rifle, as the the pre-1981 style buffer has a 0.125" pin hole. The newer rifles have buffers with a 0.155" pin hole.

Pretty sure the buffer is one of the parts that’s missing. I’ve already ordered a recoil spring and guide

The synthetic buffers are cheap, around $10 for two, but you're unlikely to ever need more than one.

I've put them in my 60s, 795, and 99M1, kind of a PITA the first time, but not hard and definitely worth it IMO.