I've put JCWitless cruise control on two cars, neither of them VW, and found
them to be at least the equal of original equipment cc I've used.  Good tight
control of speed up hill and down.  Not all that robustly manufactured, so I
don't know how they would do over the decades; I owned each for 3 or 4 years.
Installation takes a solid afternoon, maybe more.

One of them was a digital setup: tap the button five times to speed up by
5mph.  Really nice concept.

I don't drive far enough often enough to make cruise a Vanagon priority now,
but for $70-80, versus $x00 from an installer, I'd recommend it.
B.