i reckon the 6 speed evo box would be a good option, they're also pretty cheap over here. with a fairly short diff ratio, a 1:1 fifth etc it'll be the best of both - 5 close gears, and an overdrive 6th. will keep a look-out for what turns up over the summer i reckon. have enough to be getting on with for now without changing gearboxes. would be nice to know if it would fit though