Marauder WWII Vehicles?
 

I was looking at having marauders use some upgunned WWII vehicles, specifically StuG's and the like. Any tips for choosing what guns to put on them? I want them to be fairly realistic.

Would these vehicles be from unarmed private collections? If so whatever can be scrounged up. Main guns would be difficult, but machineguns, etc taken from NG armouries and the like would be a good choice.
Another option might be an old tank which was used for avalanche control - I think there's an M60 somewhere in the US or Canada employed in that role which was re-gunned for the job.

WWII era vehicles may be more trouble than they're worth given the scarcity of spare parts and likelihood of already having a high wear value. Some of course have been rebuilt from the ground up, but parts will still be an issue. Those still possessing their original weaponry may be difficult to supply ammo for - how many rounds can be still around for the old German 50mm for example? Not like many have been made recently.

If CONUS or Canada, avalanche howitzers might be a safe bet. A machinist and a list of ammo collectors would allow a sample practice round of solid shot to be reproduced. WWII stuff is rare and parts are hard to come by now. The ATF has rules regarding demilling fun stuff as well.