I've been looking on Ebay for Filters but noticed that some hav "ears" under the base and some do not. Which would be the best fit for the pro jet?

I'm sure someone who's made the swap will chime in soon, but in the meantime, check on TV Jones' website. He had some video or pictorial how to's that showed mounting methods, what if any mods to the cavity were needed, etc. I think it was under the "mods" menu. That might get you headed in the right direction while you wait for an answer from those that have already done it.

the pickups with the ears are an english mount ,,, you use the pickups w/out the ears , TV Jones are about 150 each , and regular Gretsch Filtertrons are like 108 for the pair , i went regular