[Rick Parker]

Stud mount rockers have been the norm for SBF since its inception with the exception of sled type rocker that bolted down and were non adjustable. You may want to check your rocker geometry and pushrod length as a remedy to your interferance beween the rocker and the stud. As far as benefits or reliability one VS the other, the shaft mounted once properly set up will have less deflection, especially if you are using very heavy springs. The current shaft rockers for all but the FE's were developed for Winston Cup and have filtered down from there. It allowed for increased RPMs (they are near 9300 RPM now) in unrestricted form, with a non roller cam. These guys are THE cutting edge in push rod V8 technology.
For a hydraulic or solid roller, shaft mounted rockers will have more stability, for flat tappet (solid or hydraulic) 3/8" or 7/16" diameter studs (high quality IE:ARP) will work just fine. If you use studs, try to have the majority of the threads above the fulcrum of the rocker, so the rocker is supported on the stud without contacting on the threads.