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I saw those a couple of weeks ago. Doesn't appear to actually be shipping yet (as of a couple of days ago). On the Jeg's site, it say that they add 0.54" of clearance vs. the stock valve covers. In my case, that wouldn't have been enough. I purchased a set of 0.5" spacers and those weren't enough with the stock valve covers. Disappointing, as I like the idea of these and would use them in a heartbeat.
So I expect that with a 0.5" spacer and the 0.54" these give you, everything should fit, depending on your rocker setup.
The key that I haven't figured out is the hardware situation. The 1" spacers I just purchased came with 1" adapters that screwed into the heads, and the original hardware (bolts) were used to screw down the valve covers. You would need the same thing with the 1/2" height spacers as opposed to a spacer kit which includes 1/2" longer hardware. I imagine some exist, just have to find them.
I have the Holley first design and they would not clear my T&D shaft rocker arms. With the UMI 1/2 inch spacer they cleared just fine. I don't know if they would work or not. Maybe with the Yella Terra 3/8" valve cover gasket this 2nd design would work.
Here is a picture of the Holley first design and the UMI 1/2" spacers.
If you read further on it also states: "Clearance for .750" lift cam with stock style rocker arms". I guess somebody will have to buy a set and see.
One more thought. If you do buy a shaft rocker arm kit such as Jessel or T&D and have to use shims to get the correct geometry that will take away from the clearance. To be safe I would also order the Yella Terra thick valve cover gaskets.
09-13-2015, 11:57 AM
Holleys NEW tall valve cover. 
