Originally Posted by PaGroundhog
... The Chateau has a GM 4500 chassis and a V-6 ...
Pretty sure the 4500 comes standard with the V8, not the V6... The 3500 comes standard with the V6.
That said, I would go over both very thoroughly looking for signs of leaks (roof leaks, but could also affect walls and floor - any sign of water intrusion) and delamination, and general wear and tear. I'd prefer the one that's in better shape.
All else being equal, if the GM chassis has the V8, I'd prefer that one because the Chevy chassis drives nicer. If it really is a V6, then I'd go for the Ford.