Scot, Weiand and Magansun

Not that similar.

S.C.o.T. (Supercharger Company of Turin) was a prominent manufacturer 50 years ago, and they're collector's items now and very $$$.

Weiand makes a good GMC Roots variant.

Magnuson makes (actually modifies) the Eaton end-feed Roots variant.

How much boost does he need?
How big is the engine?
What manifold does he have?
Does he already have a front accessory drive (V-belt, serpentine belt, Gilmer belt, chain)?