G'day harko, Don't know anything about Teffney crusaders, so that's a new name to me.
Is it possible the 'crusader' tag has something to do with the Crusader caravans made in New Zealand? These were imported into Australia throughout the mid-to-late 1960s and into the early 1970s. New Zealand vans have the oversized front and rear windows for see-through towing requirements over there.
The following newspaper archive tells a bit about new Crusader models hitting our shores back in 1971, and talks about fibreglass roof and ends...
If anybody knows about the Teffney name (...which sounds like somebody was sneezing at the time they were trying to say "Chesney"... ), then it will be our resident Librarian, cobber. ;D
An interesting tidbit is that Chesney were making a similar fibreglass roof and ends model in Qld at the same time as these Crusaders. Another case of somebody copying somebody else.