I wish that I could tell you which spacer, type of material and hieght and which type, four hole or open, spacer to use but I can't YET I have several tunnel rams that I want to try soon, including a Indy tunnel ram with M.W. ports for a low deck and a pair of Rons terminator throttle bodies with his injection kit using E85 The bad thing about tunnel rams and different hieght and type spacers is the throtte linkage length from the bottom bellcrank to the upper arm, I have three different length arms now so I hope they will cover the different spacers I want to try on that Indy intake I have several different spacers to try, one inch phenolic spacers like in this picture under the Holley carbs. on the Mopar tunnel ram I also want to try two sets of two inch high aluminum spacers, both open and four hole, a pair of 1.5 inch tall Wilson aluminum 4500 reversion spacers and finally I want to try a set of two inch tall tapered Dominator to 4150 adapters to use the Terminator throttle bodys on the 4500 intake top so I can mount the terminators in line instead of sideways like the way the Indy manifold tops are stock