I'd vote for finding a head unit with a 1/8" input jack as well...gives the
most flexibility and avoids the need for any 3rd party fm transmitters or
adapters...all you need is a cable.

I used to have a Blaupunkt tape deck in my '69 camper that had a credit card
remote and a female 1/8" jack on a cable.  That was really nice!  I bought a
single 1/8" > 2 1/8" y-cable and then ran a really long extension to the
back so I could control the iPod or whatever while laying in bed.

For my vanagon camper, I just found an Aiwa deck that's a couple of years
old on Ebay for $25.  It has a 1/8" jack built in to the faceplate of the
unit...works great!

Good luck.

James
'83.5 2.1 country homes camper