Not strictly true , unlike later Furys/Foundations, the B-90s were discontinued before Peavey started importing necks/bodies.
They were produced on the exact same machines worked by the same button pushers as every other US Peavey .
Quality of parts varies. Patriots and B-90s both had the basic BBOT bridge seen on most Peaveys , early Foundation-S got the old Foundation trapezoid bridge/ later builds also got the BBOT . B-90s got pretty average tuners , Patriots had decent tuners , Foundation-S had Schallers.
Pickups is where the basses differ greatly. B-90s got some run of the mill ceramic PJs , Patriots used existing Ferrites. For the Foundation-S ; Hartley had Schaller re-engineer the classic DiMarzio DP 122 & 123.