Gary,
Another thought :-
The age of your van and your measured dimension suggest to me the van is what's called the "boat roof" type of design.
The porch awnings that ideally suited these was Isabella's Combi 680, these fitted part in the awning rail and then dropped some way past the door, depending on actual size. These were "universal" awnings insofar as they fitted almost any van and were of your van's era.
If you go to this link for the 1994 Isabella Catalogue, download it and look at page 7 and 12 you will see what its all about;-
http://www.isabella.net/uk/extra/catalogues/1994.html
You ought to be able to "find" one of these second hand and they still are likely to be in quite respectable condition as they were very well made. Ideally go for one with the IXL frame rather than the steel; they made them for years and the colours offered changed from time to time [brown, green and blue/grey]
You might need to budget to have the beading replaced as this always needed to be nicked for the required drop point; doing this would allow for the latest dual bead one to be used with the pole end blocks. I know where a green one is.