How about 60X70, 8" Slab, three working bays, a rotary lift, low bay lights set at 15', fluorescent high output lights set at 10', 200 amp panel, separate wood shop completely stocked with tools and a dust collection system, 7 1/2 HP compressor with dryer in it's own room insulated for sound, air lines everywhere, electrical outlets everywhere, 220 volt outlets in strategic locations, shower room with toilet, laundry sink, outside kitchen/bbq area with refrigerator/stove/sink etc, beams to install engine hoist or crane, separate mechanical work area with drill presses, bead blasting cabinet, mill etc, R-40 Insulation on the walls and R-30 on the 32' ceiling, cable, phone, hose bibs all around the outside, outside lighting,lots of storage, office space/guest bdrm on 30X30 mezzanine with view. Priceless!
If you are going to build it Jim, make sure you get the larger width doors, one of the few changes I would make. Mine are 8' and are narrower than you think.
