Your tag axle is most likely a Henschen Dura-Torque with electric brakes. At least it was on my '85 325. It sounds like you have more going on than just an alignment issue to me. If yours is indeed a Henschen, Call an Airstream motorhome dealer ASAP and see what they recommend. I'm not sure that the average truck alignment shop would know what to do with it. If you do take it to a truck shop, I would recommend that you call ahead and ask if they have experience with Henschen axles.
AIR 2053 Current: 2006 Born Free 32 RQ Kodiak Chassis, & 1995 Coachmen B-van
Former Airstreams: 1953 Flying Cloud, 1957 Overlander, 1961 Bambi, 1970 Safari Special, 1978 Argosy Minuet, 1985 325 Moho, 1994 Limited 34' Two-door, 1994 B190 "B-Van"