Hi David,
I used the ITG race filters for this TMW 351W I built for a friend.
TWM has (or had) a link on their website for ITG. You will have to find a US distributor or, being a manufacturer, they may sell direct to you. The bottom plates mount under the air bells and the filters are attached using little 1/4 turn fasteners. ITG only sells blank plates for V-8s but somehow I don't think you'll have any problems drilling holes in aluminum
HTH,
--Mike