Yeh its a main cap girdle to tie all caps together.. The cut out is to suit the sohc engine because the oil pump is in that position.. Here's come pics of the head
as far as im aware u can run up to 10.5 without cage and 10.0 with car newer then 2003... that's going off what they were saying at woopass Wednesday last night. my mate was there running in the 10's last night without a cage or a andra license and they didn't say a word to him!!
cheers! na no caged yet, the plan is to enter power cruise in October and then gazza nats early 2012, once those 2 are out the way the cage will be put in