I am assuming the 'one vendor' you are referrin' to is Mar-k - don't they make there various parts different lengths? I know they make the metal strips that go between the planks in custom lengths(the techincal term for this part escape me at the moment), so it would stand to reason they make the bedsides longer also.

However, the cost of shippin' certainly wouldnt' be cheap.

It might be cheaper/easier if you took yer beat up bedsides(if you have them) or get the specs somewhere and find a metal fabricator in yer area to fab some up for you.

The bed side itself is so long, with the bend and roll in the top - then the stake bed hole boxes, but that is only if you want them on there.

Anyway, it is an idea.

-W