If you cant find any Crane Nitro Carb units, I am told that Elgin has comparable units and the guys at Competetion Products always have something good. I have used stock LT-1 units that have been nitrided and cryroed and never broke any.Kinda expensive to build though. I think the trick with the rockers is to get the lifter travel under control. If you stop the lifter from taking a .150 run at the rocker, the breakage seems to stop. The spec is .015, I run mine at .018 or so.
The best valve spring setup for LT-1 in my opinion, is the Comp Cams beehive setup. They have the springs (I use the stout ones) retainers, spring locators and locks that solve all problems that these heads seem to have. They last forever, even with harsh use and rpms in the 8000 area.
Jason Line told me to use as big a pushrod as I could get into the engine. I use Smith Bros 3/8 units because the 7/16 test unit I tried will not clear the port without offset lifters; not really legal in stock.
If you need more help, my email is
KVIAUTOGUY@aol.com