I have been mulling over the idea of taking out the original 4 speed gear box from my 82 transporter and putting in a later model 5 speed gearbox. The hope is that I will get better fuel economy (only getting 350-400 to a tank at the moment) and a higher max speed (right now it sits on 110 comfortably. I wouldn't mind getting it up to 125). I guess the most important question is will a later model, watercooled 5 speed gearbox fit in my '82 Microbus? Can I expect to get much better results, especially in terms of fuel efficiency, from a 5 speed gear box? Is it worth it? I've seen 5 speed gear boxes for sale on here for about $800 and I imagine it would be about 4 hours labour. Will the resulting savings in petrol cost outweigh the cost of the new gearbox? Any thoughts, comments or observations are welcome.