Mark, it depends what sort of driving you're doing. For around town 3.55 ratio would be pretty good, make the van more lively off the mark (no pun intended). But on the highway going to be doing 3500rpm + at 110km/h with standard size tyres, ie not recommended if you're on the highway a lot. Also a tonner diff is going to have a different yoke to you're van tailshaft I believe