I want to get a set of trickflow track heat heads for my 91 notch and i dont know to much about them. I noticed that i can get them o-ringed or without o-ring. what does that mean? Also it has the 2.02 valve and a set of edlebrock heads with the 2.02 valve requires the pistons to be notched. I herd with the trickflow heads i dont need to notch them. Is this true? Another thing is that they have 61cc combustion chambers, what compression shoud i get with the stock pistons? and anything else i should know about them like special parts for installing etc.. any info will be greatly appreciated.