You will have to sand down the firing pin that protrudes from the slide, sand down the Denix and Spain logo that is on the left side of the gun's lower receiver, and those are just the simple things. Additional things that you can do are reshaping the trigger and hammer, as both are bulbous and oversized, sand down the ENTIRE gun, as the casting on it is kinda crappy (Birchwood Casey Aluminum Black I've heard, is good to refinish sanded areas on a Denix), buy real Mauser wood grips (Which are really freackin' EXPENSIVE!) and reshape the grip frame to accept the grips, as the grip frame is vastly oversized, scribe in the magazine release details on the bottom of the gun, and even add a faux button release. You can also grind down the sight sphincter, as that's not on any MGC or real Mauser. From there, It's just a matter of cutting down the barrel, adding the needed parts, and boom, one DL-44!
Here's
New Page 1 for you, which details the main conversion detail, the grips. Of course, with an MGC, you can skip most of the above mentioned work, but they are really rare, and REALLY expensive nowadays. I'm working on a Denix in my spare time as well, though most people don't bother going as far as I detailed above. That's all up to you.