Thanks much to all who responded about the regulator!

It looks like a Marshall 299 is what I need. The 299 is
just like the 290, except it has the vent on the side
so it can be pointed down. The 290 would have the vent
pointing forward in a vanagon.

I'll make some calls tomorrow and try and find one locally
so I can use it this weekend.

Thanks again,
Steve