Reznor Heater, I bought it but it's too large for a normal garage. Delivery available for a small charge.
The Reznor F-200 200,000 BTU Gas Fired Unit Heater Natural Gas
Reznor F-200 Features
Aluminized steel heat exchanger
Single stage combination gas valve
Transformer for 24-volt controls
Blocked vent shutoff system
2-pt threaded hanger connections
Performance
Heating Capacity
160000 BTU
Voltage 115 Volts
Phase 1
Frequency 60 Hz
Dimensions
Flue Connection Size 8 Inches
Gas Connection Size 1/2 Inch
Product Height 40 1/8 Inches
Product Width 23 1/4 Inches
Product Depth 36 1/4 Inches
Product Weight 170 Pounds