Walt: I do believe that you should have enough space between the speaker's surface mount and the dash board, I think there is about 1/2" clearance and the Infinity 32.1cf have a 3/8" protrusion. If not, you can make a shim that is 3/16" thick. This is all you need and again I believe that the mounting studs are long enough to accommodate the shim and speaker. If you are making the new shims, have holes provided in the shims to be mounted onto the dash and also install studs to the shim to accommodate the 32.1cf. FYI. You can install up to a 4" speaker in the same space where the 3 1/2" sits with no trouble with tweeter protrusion. The dash mounts opening can handle the 4" speakers. You can use a Dremel tool to remove some material off the dash. Remove about a 1/6" around the dash's opening which will give you an extra 1/8." The 4" sounds better too, they are bigger, therefore they have a slightly deeper sound. The cost is about the same. I have a set of Polks 4" in my DeLorean for the last five years with no problems in the mounting or the tweeter protrusion and they have a 5/8" tweeter protrusion. I like the Polks over many of the other speakers that I A/B five years ago. Two weeks ago, I have replace my entire sound system components except for the Polks speakers under the dash. Due to the new equipment and its sound characteristics, I am tempted to get under the dash board and replace the Polks with the Infinity 432i (4") to get a "balanced" sound along with the other Infinity speakers that I have in the DeLorean now. BTW, on the issue of speakers, they are very subjective, to different people. I may like them, you may not. So, listen for the "characteristics" carefully before you buy and they do sound different with in different cars with different equipment driving them! They may fit the car and not your ears. Kayo [Non-text portions of this message have been removed]