I converted my 355 sbc to hyd. roller. Used comp cams parts.
you have to get the retrofit hyd. roller lifters. (at the time I
did mine the were hard to find.) Have to have proper springs,proper pushrods-length depends on alum,cast head. Also deck height
comes into the picture. The comp cam I used has a cast dist. gear
so a bronze gear is not required. If using a mech.fuel pump you need a special pushrod for that also. You have to have a thrust buttom and check endplay.(on the engine stand is the best place to do this)I also installed a stud girdle. Could have done without this as my cam is not wild. Just wanted the insurance. If going for high rpm I would consider the rev. kit from AFR. maybe others out there by now for
hyd.rollers. Have had running for over a year now ,no problems ,driven everyday and glad I did it-expensive though. I used a gear drive with a bronze thrust also but a chain with a thrust of some type would also work. pm me if I can be of some more help