[OrrieG]

have you considered an attic truss for the upper storage? That is what I used. Then you could raise the ceiling to at least 9'. 8' makes it hard to get a cab off and over an installed engine. If not you might use a vaulted truss to get ceiling space above, or even hand stack it. Have a couple of the trusses at each end (in 6') designed for lifting. Put in plenty of outlets, design the panel for a couple of 220 (compressor, welder). Same with air so you aren't running hose and extension cords all over the floor.