You should be able to find the 6 cyl PS pump/alternator brackets in '60s and '70s cars. Look for full size Chevy's, Camaro's, Nova's and Olds Omega, Buick Apollo and Pontiac Ventura as they all used the Chevy 250 six engines. I find them to be much more common than 6 cyl trucks with PS.
I used one from a Buick for my 292, but it had to be modified for the taller engine. 292 PS brackets are extremely hard to find.
