The three Shures I can think of, are the 57, 58, and 545. You can probably pick them up cheap used and gut them for the element and transformer. Last one I did, I ordered the element (a 545) through a music store and saved a bit of time.
You can wire it either high or low impedance. I prefer high, because I use a beltpack EQ/volume, then into a wireless pack.
Steve
Thanks guys..for the help.. all very welcome.. I've taken notes and am taking my boxes in to my tuner in a few months to get amplied.. he's never worked on amping Cajun boxes so everything helps !
G.