Stefrobrts, As you live just north of Vancouver near Battle Ground your weather is much like mine. So maybe this will help. Hope so.
I have a 40' X 40' X16' shop. I have used a wood stove for years. When I was building parade floats ( up to 10) a year I used about 8 chords of wood. Now that I have retired I use the wood stove to "recycle" the junk mail and the household paper that would go to the dump to get buried. I just installed a new heat pump in my house and am now installing the old electrical furnace in the shop.
I will be placing the furnace on a platform suspended from the wall so the "air box" on the bottom of the furnce will be at 7 feet above the floor & in one of the shop's corners. This will allow the air from the furnace to blow in 3 directions. It will also allow the furnace fan to circulate the heat from the wood stove if the junk mail gets to darned heavy by just using the "fan cycle" on the thermostat.
As I only want to take the -FROST out of the air, I do not think it will cost to much to operate. I only want the temp at about 60 deg. F. unless I am painting or some such thing.
As I just had knee surgery last week, all projects are on hold for one more week.
Then it is "look out shop and AS".
I will post some photos when I get it up and running.
I am using the old electric furnace over a propane fired furnace for 2 reasons.
1: I already have it
2: Propane cost is higher than electricity . I filled up my propane tank for the house hot water heater in July and it is costing me $75.00 per month for a total of 11 months total. And that is just for hot water. I am looking at a new electric hot water tank soon. When I built the house I wired & plumbed it for both electric and propane water heater, kitchen range, furnace. And a free standing stove for when the power is out , maybe 2 times a year.
My power bill , even when the shop was running was only $250.00 at the highest. Now only $130.00 and under. Summer months only $80.00 or so. And I have a 2500 gallon pond system that runs 24/365 and runs about 3,000 per hour through the filters. The pond's cost is $8.92 per month now.
Check with some of the HVAC shops in your area and see if they have taken a furnace out of a home that is getting a new heat pump. One that will meet your needs. A lot of the time' if you say please, they will give you one that can be had for next to nothing. Remember that they are going to have to send it to a scrap/recycleing yard anyway.
Just some ramblings of an ol' fart