I am rebuilding a 396 for my 68 Camaro. The question's I have are: 1) how do I measure the clearance height of the engine. I think it is from the center of the crank to top of the air cleaner? 2) What is the min clearance of an SS hood and Standard Cowl hood? I don't want to use an air cleaner that looks like it came off a lawn mower.

I don't know if this will help you but my 68 has a steel cowl hood, big block, performer intake, 1" carb spacer and a 3" element with 14"drop base air clean, and It is really close but it fits.

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68 468 700R4

My original 396 setup had an SP2P manifold (same height as Perfomer), BG/Holley 750, 14 by 3 drop base (7/8 drop). I tried to install a 1" plate and the stock SS hood hit the air cleaner on the hood braces that run front to back. That is as far as I tried to go as the next hood was a 4" Harwood and everything fit fine then... sort of...

I also have a 68 SS 396. After I put on an Edelbrock Performer RPM with Holley 3310 and drop-down style air cleaner, I couldn't close the hood without using a 2" air filter. Unfortunately, the 2" filter doesn't do crap because the top part of the air cleaner hits the float bowl vent tubes so it doesn't seal. I thought about cutting the tubes down, but that would only leave about a half-inch of clearance between the top and bottom half of the air cleaner which will restrict air flow into the carb. Just my experience, good luck.