I have a bone stock 22/45 Target model with a 5" bull barrel. I like it ok and its crazy reliable for a rimfire pistol, but its very nose heavy with the plastic frame and bull barrel. The trigger and sights are also kinda meh. Mine is the type that does not accept different grips.

I pulled the trigger on a Dead Air Mask (wont receive it for a loooooong time) and I want to get it set up for it, or should I sell it at a loss and buy a LITE? I suppose I could get mine threaded but I'd have to send it somewhere.

I see that there are also aftermarket barreled uppers for it. I'm sure these are more accurate, but thats not really my gripe with the pistol as I'm sure a stock 22/45 can out shoot me.

The gun I have was a present from my wife so I'd rather not sell it unless it just makes no sense not to.

What should I do?

I would go for the Lite. Can you keep it and buy the Lite too?

I was in you're shoes, had a beautiful hunter model, got a can and picked up a lite. Hunter never came out of the safe after that. Eventually sold it.

I'd get a new mk4 lite or mk3.

My wife works for the company in Minnesota that makes frames for the Mark IV and mag base plates as sub contractor for Ruger.  No employee discount though.

If it's not going to cause an issue with the wife sell it and get the lite..........

Once you get the can more than likely you will have virtually no interest in shooting without it.

There are plenty of videos on YouTube on modifying your grip frame yourself to use the newer MKIII grip panels. The VZ grips do a lot in controlling all that out front weight. Then you could take it to a local gunsmith and get it shortened and threaded for the can. Here's one I have but it's not threaded, I just like short barrels.

I'd get it threaded +/- on barrel shortening.  I like the added weight in a 22LR.  That and a DA Mask, gonna be sweet.  

When you get it threaded, get some better sights.  

I don't like the Lite models.

I shortened and threaded my 22/45 bull target. While it is fun to shoot with a can. The can is pointless shooting at an indoor range. (Others shooting)

Something that is fun is a 22 comp. I have the popular one on rimfire central. It really makes a difference. The red dot stays on target. You can mag dump with all shots hitting the bullseye.