Would it be alright to use something like a silicone gasket maker in place with an existing old intake gasket on the top intake plenum?

 

The problem is that they are both machined surfaces. If everything is true, then it tends to squish out the silicone and then it's like it was never there.

I would just spend the $16 and get a new gasket set. It's easier and will be better in the long run.

You could try it though, I'm sure there have been some people here that have had some sort of success with it.

 

Would this be the right gasket set to purchase? Do they make just the plenum gaskets separate?

http://www.partsamerica.com/ProductD...pe=102&PTSet=A

 

You can get the plenum gaskets individually. Or you could just use some silicone gasket maker, but don't use them together. Solid gaskets seal much better by themselves.