Some bits of personal experience:
1. Crane gold 1.6 roller rockers fit with no mods on stock heads with stock valve covers.
2. Those same rockers also fit fine with L35 heads and stock valve covers, but you'll have to replace the rocker studs (either the metric-to-3/8 adapter studs, or have the heads re-drilled for SBC studs).
3. Those rockers will also fit on L35 heads (with replaced studs) and Vortec valve covers, but you will have to clearance the inside of the covers a little (a dremel sanding drum works very nicely).
4. Comp Cams Pro Magnum 1.6 roller rockers fit just fine with Vortec heads (redrilled for SBC studs), Vortec valve covers and a Comp 412 cam (.533 total lift at the valve). The valve covers require some slight clearancing with a dremel, but not much, and less than the Crane rockers would. As I've said before, NO SPACER IS NEEDED with the Vortec heads and valve covers with the Comp rockers -- anyone who doesn't believe me is welcome to come take a look at my Ty, 'cuz that's what I'm running.
5. The Crane rockers don't seem to hold up on vehicles that aren't driven often. I had to send my first set back to Crane for replacement, because the trunnions had galled under the roller bearings. When I asked why this happened, they said that they see it fairly often on vehicles that aren't driven much because the oil drains out of the bearings while the vehicle sits, and then the bearings are dry when the vehicle is started. Not sure I totally believe that, but that is what I was told.
![Quickstop [UK]](/forums/data/avatars/m/5/5165.jpg?1570199786){kind=avatar}
