There is another alternative, I have done one car this way . . .
There is a company in PA called Reddi Strip . . . They can remove all paint, undercoating, and any rust along with any non steel part left on the chassis.
The process does not use acid, it is done in a bake oven, wash tanks, pressure washing and a final zinc enriched wash to protect the bare metal from immediate oxidation.
Much better than an acid bath, and very effective.
That said, I feel I need to warn you as to what you're getting into. Refinishing and striping an E9 for this is not for the faint of heart or anyone on a budget. There is extensive body work and paint work required to prep a car for paint after this process. It takes alot of work.
I'm happy to discuss my experiences via phone, just call me at my shop during work hours
Mario L.
www.VSR1.com