well i made a long post and it was lost . but i been at this for 30 years building BBC and have a engine machine shop so i machine them as well as sell new and used race parts. i used just about everones roller rocker stud mounted and shaft mounted race stuff for cams past 750 lift many times . every cam you can put in a bbc. very few time were the ARP studs or stock would not work on a all iron heads with all rocker arms i ever used. sound s like to me you rocker trunnion is not facing up so poly nut not seating in the spot face .or push rods are off on length for you PRW rockers arms i a dealer for them never used them or sold any to any of my customers so i can not say if they need a tall stud should ask you machine shop guy . i would think they should not