If you can't rearm the turret or it's jammed, etc, you could always do what they did in WWII: Remove it. Some recce units did this. It lowered the silhouette and the point was to go look and see and not fight if you could avoid it.
Photo here
http://www.armouruk.net/images/us10165.jpg and here
http://farm4.static.flickr.com/3120/...4733f8.jpg?v=0 of re-enacters versions.
In Yugoslavia Allied supplied M3s or more likely I think M5s had their turrets removed and replaced with captured German guns. I can't get access to the photos from here but try Googling "stuart tank yugoslavia". 75mm anti-tank guns, quad 20mm AA, etc, were all fitted.
(Keep going down this page
http://forum.heroesandgenerals.com/v...=8544&start=20 for a couple of photos).
I've also seen a line drawing of one with US quad .50'' AA guns.