I have two benches on wheels (locking castors), the tops are large (30" wide by 78" long) hollow doors (very flat), with 30" high bases made from 2x6 and 2x4's. Both have shelves underneath. Been using them for 20+ years now, very handy. I can send pics if you'd like. My only complaint is that there are times the benches are not long enough!

I can second the overhead air and power outlets. I have both power (4x outlets) and filtered/dried air every 4 feet over both benches. Extremely handy to have, if you have the skills and the hardware (large compressor and sufficient power panel/breaker capacity) to allow it.

Barry