Restore factory ac or go aftermarket
... I looked at boucillion's a/c bracket, but it seems to use a 'short' sanden compressor that isn't as readily available as others ...
At any car show, you will see almost all resto-mod cars use Sanden compressors. Many Chevy guys use several shiny chrome turn-buckle pivot mounts. You might adapt to any engine similarly. But, the Bouchillon (and others) brackets are easier. Sanden's do come in different lengths, I recall an SD7H12, H13, H14, & H15. I think the H15 is most common, and the H13 is what rodders call the "shorty". These are the later 7-bolt type. The earlier ones were 5-bolt, w/ PN like "508". Don't get hung up if labeled for R-12 or R-134A since you can drain whatever oil is in it. I use PAO 68 oil since it works with all refrigerants and mixes with all oils. You can also change the rear heads to get whatever fittings you want (~$20 ebay). Most rodders use #6 & #8 O-ring fittings. If worried about a spare compressor, buy 2. I have bought new Sandens for $50 on ebay, in the Fall & Winter, but you missed that this year.
Re controls, might be easiest to use the factory under-hood expansion valve, though you could fit a modern block type. Also, add a low/high pressure switch. You simply wire it in the compressor clutch circuit. You can also install a little PRV on some Sanden heads for emergency vent (>290 psig?), but perhaps illegal for R-134A. BTW, note that the later will soon be discontinued. I use Duracool, but that excites many people.