Build ANOTHER garage for all the stuff!!...
It would be best to build another building,just for the tools and other junk!..but its possible to keep everything under one roof,it just takes a lot of space away...my garage is considered "huge" by many who see it..but inside,its not very spacious anymore,thanks to the "too much is not enough" syndrome...
I can tell you what NOT to do!..having much the same size quonset as yours,I'd NOT line both sides with benches,pallet racks for shelves,and a drill press,furnace,set of drawers,and piles of metal scrap,1000's of cheby parts,and tools,firewood,stoves,table saws,etc!...my garage is 20x40 with 13' height,but I am only able to fit ONE vehicle in it,thanks to all the other stuff!..

I am too much of a pak-rat I guess...
I'd like to build a platform,or "upstairs" in my garage using the 2 pallet racks and the "roof" of a small "office" in one corner I built as the "legs" to hold it up..(the "BTU" room,4x10 with 8' ceiling and a big wood stove--was going to put a compressor in there,but I decided I needed a hideaway more)..
I would put the compressor "upstairs" if it had to be inside at all..outside is better,much quieter....but if I had a platform 8' off the floor about 16' long,I could hoist my engine crane,engine stands,floor jack,and store much of the other stuff cluttering up the floor and gain a lot of floor space..you would not be able to stand up on it without bashing your skull on the roof though..bummer!..
I'm considering scrapping the furnace..its an old forced hot air clunker old as I am,I had to weld patches on the firebox so I wont be suffocated if I used it..but its too costly for fuel,it needs a control unit,and I prefer the wood stoves,they get it warmer than the furnace,and wood is free and good excersize to gather and cut!..I'd gain 5' x 3' if it were gone,and I might even get a few bucks in scrap for it..
I agree 100% about putting EVERYTHING on wheels!..my table saw,firewood carts,torches,welder,air compressor,and pretty much everything else has wheels on them!..its nice to ROLL 300 lbs of firewood outside with one hand if its in your way!..I use a utility trailer sometimes, if I have a lot of wood,and just wheel it outside if I need the room back..
