Andrew -- if you can stay in Oregon to do your work, that is good, since you will not be charged sales tax for your materials, and finding welders ("fabricators"), etc in the rural areas is fairly easy (and at better prices than California.)
Isn't there a van customizer near Quadvan? Name something like Performance Vans? I've been wondering about using them, someday, for a custom conversion after Quadvan....eventually....
You may be able to find space in some rural areas right around Portland like Molalla or Sandy or Boring.
-- does Eugene have a "Tool Lending Library" like Berkeley does? It's great -- members can check out the tools they need for a few days.
Or does either Eugene or Portland have a workshop-for-rent-by-the-hour sort of facility? Denver has a great one, called "Club Workshop" http://www.clubworkshop.com/
with wonderful powertools and facilities.
(I sure wish Austin had such a place -- I'm trying to do a van build sneakily from an apartment....)