I didn't have a van back then, but a friend got one ('74 GMC G30 shorty) that had a mini-fridge sized cabinet right behind the driver seat full of home stereo equipment including two items that I feel truly represent '70's stereo equipment:
A TEAC reel to reel tape deck and a Heathkit stereo reverb/time delay "sound shaper".
The tape deck may not fit your plans and car audio time delay units may not have been available yet (i got a Alpine unit in '78), but reverb units were.
Last edited by vandude360; August 13th 2012 4:53 am. Reason: can't spell