... but it took forever to heat the shop up...........

Ref my previous post about reclaimed forced air furnaces. I had a forced
air furnace in a small shop years ago. The furnace came from a 1,200 sq ft
house and I was using it in a small 250 sq ft shop. When the blower came
on, the windows literally rattled. It would take the temp from 30 degrees
to 65 degrees in 15 to 20 minutes. Metal things, like table saw tops, etc
stayed cold for a while but the furnace worked well, to say the least.