Humor aside, the bottom 3 sheave pulley is supposedly a OEM 67 A/C equipped pulley. The top one is what came with the A/C kit (seems very well made too). Should I go with the original which will drive the compressor faster or the kit supplied pulley which will run the compressor slower?

Lets see if I understand the question. You have an OEM pulley that was driving a big honkin’ cast iron piston compressor and you have a pulley that came with the A/C kit to drive a small, efficient aluminum compressor. So, the question you are asking us is whether you should void your warrantee on the kit by not using the kit pulley?

Looks like they're gunna be driving the water pump the same .... and maybe even the A/C the same .... depending on diameter of kit A/C pulley, versus factory A/C clutch.
One's built for the other, a matchin' pair.
If your friend wants to ditch the Sanden type for a Tecumseh/York type ... use the original. 
 

OEM Pulley out, Kit Pulley IN. I get it. 

I prefer the smaller crank pulley and a slower driven compressor.
My ac works fine at idle.  At highway speeds, it is surely spinning fast enough, but all the air leaks in the cabin make it feel less than perfect.
As long as the radiator fan speed is sufficient it will be ok

If'n it were me I would check the operating speed of the compressor. When I switched to the aftermarket supplied compressor I went through two of them. After getting tired of cleaning out the system I did some research and found out it was running too fast and tearing it self up. The allowed speed (RPM) is not based on pulley size.