You can do it either way. On my last engine I used the rubber seals. On my new engine I did not use them. Reason being, I bought ported heads and intake, plus with my block being decked a little bit the rubber end seals would have held my intake up too far. I could have milled the ends of the intake down but I didn't. Im to cheap!:biggrin:
If you do go with sealant on the intake end rails I would reccommend The Right Stuff. This stuff works really good. Alot better than regular RTV.
Just my $.02