Max lift/stock slugs

One more question, on the RPM intake there is a odd threaded hole at the front of the intake with a odd 5/16 x 18 thread count. What was/is this for? Seems like a weird size to me. Nothing on the stock engine was bolted there.

If it's the LA air gap you're looking at: Mine with the LA patterned EQ heads,drivers side above number one,I used it as a universal throttle spring bracket mount. My pro products,came the same way.