You might try a "Group 41" battery. Came with Audi 5000's under the rear
seat, so the gas's needed a vent. Fits the Vanagon box, and has the same
post arrangement, as a Group 42. The Diesel version has 850 CCA, and will
spin a 2.1 pretty good. You will need to drill a hole for the hose, be sure
and paint the edges, and use a grommet to seal it from the elements. Aim
your drill well !!!

Skipper

>Very few available batteries have the vents on the ends to vent hydrogen
>gas to the outside of the van.  Frankly, I don't even remember the brand I
>have, I would have to open up the compartment and look.  But it has the
>vents.