Howdy Neighbor,
A few popular brands used here on GJ. Mr. Heater Big Maxx, Modine Hot Dawg, Reznors etc..
Big Maxx usually has lower best price and has good customer service.
I'm using the 75k btu Big Maxx in a 1000+sq/ft. The newer model is rated at 80k. Northern Tool usually has the best price but I don't think their carrying them at the moment.
Research your heater and vent location and type (vertical or horizontal) as well as your gas line install.
Your heater should blow in the direction of your largest cold air entry (service door).
Consider/inquire with your town codes as well.
I know here in Chester, to get a permit you have to hire a licensed installer and the fire chief needs to inspect.
I hung my heater and did the electrical and thermostat as well as scoped out the proper location for the vent/gas runs to make sure they were suitable for the install/inspection.