"...You can helicoil the rocker stud holes and install 7/16 studs. The special helicoil tap will work in the old rocker stud holes, no need for any drilling..."
Are you sure ?
If I remember correctly, everything I've read here has indicated that you can tap the stock holes for the 1/2" bottom thread ARP studs, but a larger hole is needed for heli-coils. ???
http://forums.maxperformanceinc.com/...7&postcount=13
I've never done it. So, I'm just going by what I've read.
Several have posted that if you go with the 1/2" bottom thread ARP studs, you must remove some of the bottom threaded portion, because that portion is too long, therefore will bottom out in the hole. Don't know if a thick hardened washer, under the stud, would work, instead of removing stud material, or not. ???
" 15 heads (sometimes referred to as 215)..."
The 455 Ventura bracket car I bought had "215" heads on it. And, the numbers cast with the heads was 215, NOT 15. So, they may have been VERY similar. But, there were some heads that had a 15 casting number, & some that had a 215 casting number. Maybe one was used earlier in the model year than the other. ???
http://www.wallaceracing.com/enginesearch4.htm