Jack;
My two cents.Check with the local or municipal building dept.The trailer may have been located under a building permit in which case they would have records.May even turn up a set of construction specs.,foundation details and septic info along with any problems.Was an occupancy permit required and if so was one issued?Up here we keep this info as public domain.
Trailers here are constructed to a CSA standard which is referenced in the National Building Code.Older trailers were pretty lightly framed,some with 2x2 studs,etc.The newer ones come close to the NBC standards for residential housing.
A bit of investigation is in order.
Good luck;Earl
"Always keep an edge on your knife,son..."