I have a Ten Tec Scout coming in and the mobile HF itch needs some scratching.  The antenna(s) that I plan on using are High Sierras copy of the hamstick, working initially 17 and 40 but of course there are questions.
I can install a thick NMO mount towards the back of the roof, then use an NMO to 3/8-24 adapter for the antenna, but the height may hit 13+ feet.  Ok, another option can be the rear bumper on either side of the taillights with a bracket to distance the coil from the metal body.  I could also do the same with the front bumper. Pros/cons?  The most interesting idea would replace the stock factory radio antenna with a 3/8-24 mount on the front left fender.  Another option right around that area could involve a bracket coming out from the fenderwell right above the tire with the antenna mounting a bit out from the sheet metal.  Those of you that have or have had mobile HF rigs of a fairly simple nature, how did you get started?

On both of my suburbans (92 and 2002) I mounted a hamstick QD on the bumper. Performance has been good. Ideally, the roof would be better, but the height could be a problem. I also used a piece of para cord tied around the top of the fiberglass section, keeping the antenna from flopping all over the place.

Use an auto tuner to feed a 102" whip on the rear or front bumper.  Then tie down the end for NVIS :)

Worked great for RX, sucked Ass for TX on anything but 10M.