If you're already geared for burning wood, why not put the wood heater outside in a box, insulate the box and pump the air from the shop into the box and let return into the shop as hot air? I heated the shop I was renting years ago like this. BTW, I could also cook a whole chicken in the duct coming back in the shop if I kept the fire in the heater stoked up. Yes it can get that hot.
Back to the subject of the fan/radiators you have, Look up the specs on what you have. I had some that were for use with either steam or hot water. On steam they were something like 100,000+ BTU, on hot water they were only like 12,500 BTU. I'm guessing you have to run that hot water heater a while with the water temp around 140*F to heat your shop.
I ran 180* water through the ones I had and it still felt like it was blowing cold air unless you got right up in front of where the fan was blowing the air out. I took them out and tossed them. I was better off with just a copper coil section sitting there with a box fan running on low. I'm sure the other elements put out more overall heat, but they were a PITA with the fan noise and cold air feeling.
