Wayne,
I sized my A/C system as the smallest they had, the Mini Gen II from Vintage Air. The compressor is a Sanden unit and the back of the compressor is even with the first head bolt about an inch beyond the face of the head. I don't know about the engine compartment of your car but with the DRB 40 the engine bay WAS a sloping surface from 30 inches(there about) at the top to a narrow 18 inches at the lower frame. Here is a pic of the original with the rear part already cut away.
I didn't like this arrangement when I started my build along with the welding of the steel panels on the car. I removed all the panels and replaced them with stainless and better welding. In the engine bay I removed the sloping panels and squared them off leaving a shelf arrangement.
This gave me a lot more room to work with, and it still left me with a 4 inch alley way to the rear of the car for the wiring.
and allowed me to do the alternator and compressor this way. Otherwise the engine would have sat much higher in the bay. and the clearances much tighter. The engine was moved slightly forward and the alternator which is on the front pully grove is 2 inches from the firewall framing and the valve cover is 1 1/2 inches from the top frame rail.
I don't think you will find a smaller compressor than the Vintage Air unit. There may be smaller interior units without a defroster or accessory, but not a smaller compressor.
Bill
I sized my A/C system as the smallest they had, the Mini Gen II from Vintage Air. The compressor is a Sanden unit and the back of the compressor is even with the first head bolt about an inch beyond the face of the head. I don't know about the engine compartment of your car but with the DRB 40 the engine bay WAS a sloping surface from 30 inches(there about) at the top to a narrow 18 inches at the lower frame. Here is a pic of the original with the rear part already cut away.

I didn't like this arrangement when I started my build along with the welding of the steel panels on the car. I removed all the panels and replaced them with stainless and better welding. In the engine bay I removed the sloping panels and squared them off leaving a shelf arrangement.

This gave me a lot more room to work with, and it still left me with a 4 inch alley way to the rear of the car for the wiring.

and allowed me to do the alternator and compressor this way. Otherwise the engine would have sat much higher in the bay. and the clearances much tighter. The engine was moved slightly forward and the alternator which is on the front pully grove is 2 inches from the firewall framing and the valve cover is 1 1/2 inches from the top frame rail.
I don't think you will find a smaller compressor than the Vintage Air unit. There may be smaller interior units without a defroster or accessory, but not a smaller compressor.
Bill