I've had good luck with a 1" thick 4-hole spacer under my Holley, and I'm wondering if anyone here has tried a 2" thick 4-hole spacer?
If 1" is good, is 2" better?
... Assuming that hood clearance won't be an issue.

 

There's an awful lot of variation among carb spacers when it comes to power gained or lost. Basically the only way to know for sure is to try it. If it's cheap and doesn't require hood modification, then give it a shot. If you have to use a hood scoop, I'd say don't worry about it. It'd only be worth a few horsepower over the 1", not worth the hundreds of bucks for a new hood.

 

Yup, it's a tuning aid; there's no "always right" answer, just experiment and see if it helps your particular combo. Every motor/car is different.