Welcome Slimjim,
It looks like you have a conglomeration of Jeeps. With that being said, that isn't a bad thing at all. To put things into perspective, the following link is a history lesson on what happened through the ordnance remanufacturing process;
http://www.ewillys.com/category/ordn...anufactureing/
In short, the process of the ordnance remanufacture is to strip the Jeeps down to their sub assembly parts, inspect, then recondition as needed. After all of that, the parts are placed in a bin of like parts, then the parts are pulled to rebuild the next chassis in line. It is not uncommon to have a GPW engine with a Willys frame and a GPW body. Basically, the commonality of the part fitment lends itself to throwing the assorted parts into a big bag, then the parts are shaken up then grab the next part at random. Yours appears to be a GPW frame and engine, then the body tub is a newer CJ3A or so, reproduction tub, or a very clean original. The photo enclosed is of a M38A1 frame, but the machine gun mount is intact. The front axle looks like it might be Civilian. The determining factor is that the WWII military Jeeps, (MB/GPW) had the drag link run through a mount on the front axle rather than the Civilian Jeeps having the draglink mount to the frame cross member. The link below shows the GPW axle.
https://fordgpw.wordpress.com/2018/0...d-brake-lines/
As far as the heater, I couldn't find anything on it either. More than likely, the heater came out of a truck and was installed in the Jeep. If I do find anything, I will report back with the findings.