You'll destroy any metal sandwiched intake gasket if you try to enlarge the intake ports. If the heads are CNC'd you'll not find a off-the-shelf intake gasket that'll fit.
Like the Eboks I think Keith has Cometic making custom "composition" intake gaskets made for the porting on his CNC'd BT heads. These are superior to his paper gaskets he used to have made. If so, get some of the yellow weather strip adhesive (called: Gorilla snot
). Apply a coat of it to the heads and then apply a coat to the head side of the intake gaskets. Let dry a bit and then stick the gasket to the heads. That WILL prevent gasket creep. On the intake side of the gasket you can apply a very thin coat of The Right Stuff or RTV and place the manifold.
You might also want to set the intake on prior to gasketing and check clearance all the way around the head/gasket sealing surface with a feeler gauge. This will ensure your intake will have uniform gasket "crush" when torqued.