For smaller overall size than aluminum, I made cam followers from 4140 steel alloy. It's easy to machine in pre-heat-treat form; had them treated to 49 Rockwell-C afterward. I purchased the rolling elements (wheels, tip rollers, axles) from Ron Iskenderian because I wanted to use the original non-needle wheels. Ron shared with me the factory process of coining the wheel axles (ends aren't hardened) into their EZ-Roll lifters- I built a small jig to coin them into my followers. The Isky roller tip axles use Circlips. I'm presently doing spin-tests of the OHC assembly, with no faults so far (springs are 290# seat, 590# @.686" lift) to about 6,600 [engine] RPM.