I work in a 32'x40' pole building which is insulated and wood product(OSB board) paneled. It is primarily a well equipped wood working shop w/ central dust collection I built in 2009. I use what Dave has mentioned, a ceiling mounted Modine "Hot Dawg" propane heater with atmosphere venting. They are not cheap, around $2500 installed, but worth every penny. I keep the thermostat at 50 degrees when not working just to keep glues and finishes from going bad, & lumber stable. With this set up in eastern PA, I would say I average around $300 - $400 for propane a year. I think the one thing that would give you problems will be the block, especially if 2 sides are below ground level. When I started woodworking as a teenager, I used my Grammy's block garage. Everything would take on moisture, surface rust, I would build projects only to take them in the house and watch them self destruct. I would go with Clear Spring"s set up and get some tongue & groove or paneling put up to help with the moisture, or at least seal the block good and maybe run a good, safe heat source in winter and a de-humidifier in summer.