Theres loads of different ratios available in factory boxes. Either get yours rebuilt for £5-600ish or look for a 2nd hand box.
All the ratios are here:
http://www.brick-yard.co.uk/VehicleSpecific/T3/info/gbx.htm

 

Good stuff, just what I needed, cheers

 

you could go for a longer legged box like an AAP.
It still wont turn your bus into an amazing long legged motorway cruiser, but it has the best standard final drive for lower revs at higher speeds... you'll probably see 5mph more at the higher end of your rev range in 5th depending on your tyre size. Whether thats worth the price that people ask for a used (unknown) 4.57 final drive box is up to you... not good value in my eyes.

Taller rear tyres will also help.

You dont say what box you have now, or in fact what size rear tyres you have...

Ive just done a lot of messing with gear ratios and final drive ratios, as I'm having my box rebuilt. Ive gone for a 4.14 final drive... which to buy was more than the price quoted further up this thread for the complete rebuild
To me thats better value than spending £500+ on a used AAP that could explode in 1000 miles.

 

Who's doing your box for you?

Most AAP's I have come accross recently havent even had a 4.57 in them when ive opened them up,they are also the weakest of the lot.

 

Bears Motorsport are doing it, Aidan was busy and recommended them.
I got the r+p from Germany.

Cant wait to get it back...

 

jonnyg, so you've just got a 4 speed on you DG?

spannerboy, isn't the 5 speed box a different length than the 4 speed? Something about the position of the front mount?