Do you have the Mach system door sail speaker covers? If not go, to a salvage yard and see if you can get the whole unit. Speaker grill and tweeter assembly with the plastic door mount piece.
I just replaced my door speakers with a pair of Pioneer seperates . I used the stock tweeter mount. Since the aftermarket tweeter was smaller than the stocker I traced the outline of the oem tweeter (has an integrated sort of oval bracket if you look closely) onto 1/2" mdf, cut it out, and was able to mount it into the stock plastic tweeter mount rather easily.