The challenge with the v-belt stuff, especially single, is building enough boost. Even the serpentines can slip badly at higher boost. I think the best you will generally see with a v belt is about 6-8 lbs if the belt is zonked tight. If you can talk him into a more modern intercooled and toothed belt it will make more. However if he wants it for style and a good kick in the pants, the Shelby copy stuff is real pretty in a period correct car
Back in the early '60s, I bought a Paxton for my '54 Customline/312. I next bought a '64 Custom/427 and a bit more than a year later I traded it for a '65 1/2 Mustang to which I added most of the Shelby mods. I transferred the Paxton to it. It was an unusual model---looking rather like a Mopar alternator that had been 'squashed' so that it was larger around but only about 7-8 inches from front to back. It had fins both front and back radially and the boost control pad on the front, ordinarily holding a mechanism that used oil pressure to regulate boost in the usual set-up was simply left unmachined. The housing was made of magnesium and the impeller visible inside the inlet side had more vanes and were of different shape.
I ordered a boost gauge from Gratiot Auto Supply, but it never did come in. However, blow-through set-ups require a boost reference to the fuel pump so that the Holley in the box gets the four pounds-or-so that's ordinarily necessary, and also an increase in pressure so as to make sure the fuel continues to flow under boost. A hose runs from the box to the back side of the diaphragm in the mechanical fuel pump to supply the addition.
When the blower went into boost mode, you could see the pressure rise in the 20 pound fuel gauge. Since I was pegging the fuel pressure at just beyond 3000 RPM, I always thought I was getting at least 16 pounds of boost---and probably more since it was common to turn the '306' HP 289 to 6500. I can tell you that a 396 chevy 2 at a nominal 375 (really 425) HP was easy meat. (My car weighed 2880 with the removal of the back seat and the addition of the 'glas back deck. I also used a 3.50 gear in the back and could use 1st gear at a roll-point where other cars were already needing to be in second.)
The drive belt was a very wide 'V', likely over an inch wide. I was told that the Paxton was something used in some of the competition 'blower' '57 T-birds. A pair of them, if you could find them, would be period correct and easily feed a nice-sized FE engine.
KS