My question is, what are the things I should look for that are specific to
the WBX vans that don't apply to the AC? It sounds way more complex a piece
of machinery.

You know, it's not really. The 1.9/2.1 are really just T4 engines with
water cooling and no tin-look at both type engines side by side stripped
down and they look almost alike. Certainly there are more complexities to
the Vanagon over the Bay, but nothing really to be that scared of. My
recent experience of pulling a seized 1.9 out of my '84 and converting a
2.1 over to 1.9 FI and cooling was one hell of a learning experience. After
that, I'm not nearly as fearful of the Vanagon engine/cooling system as I
was before.    Jeff