Which AC compressor for r134 AC?

[Awann99]

I bought all the factory stuff I need to convert my heater truck to AC. I was going to go with vintage air but wanted to be able to pull in fresh air because the south is very humid.
Anyway. I think I have figured out most of the stuff I need to do a r134 conversion when I install everything. The only thing I am still up in the air about is the compressor. I was looking at an AC delco A6 compressor from rock auto. Would that work without pulling too much HP away from my engine? Is the sanden a better option? Any more options? I want to be able to stay the coolest and use as little HP as possible. I’m pulling 16.5 mpg at 70 with my 350/sm465 307 rear right now and would I like to not take it down too much by adding AC.
I also will usually drive the truck at 1300-1500 rpm in town. It just putts. I drive it like an old man (no offense to any old men). Would the A6 even work well at idle or low rpms?
Thank you.