I had my tow hooks custom made by my cage builder in Columbus, OH. Real simple - welded a ring of round bar onto a substantial flat metal bar, welded that to the frame, one in front and one in back. Front protrudes from a stock opening in the air dam, and the rear comes out from under the rear bumper.
Transponder - look in the classified on this forum, ebay, or just do a goggle search on AMB transponders. I believe I got mine from Florida Region. Model is a toss-up. We had issues with hard-wired transponders in Indy cars in 1989 and went with rechargable - but were religious about recharging them. When it came time to get mine, I went hard wired and wired it into the output side of my master switch (don't have to remember to turn it on!). Mounted the unit on a bracket under the car, behind the front bumper (clear path down, and in a place where I can see to pilot light). I don't even think about it anymore.