I am going to have my spare box rebuilt, what ratio should i go for. Engine is 2.1 zetec turbo with 320BHP max torque at 5800 RPM.
Thanks Kev.

Go for a high first at the very least . Who are you getting to do the box, might be worth asking them?. How's the motor home?

Thinking to get BGH to do it, motor home finished and runs great.

You've got the power to take a high 1st depends on wether you want a cruising 5th or a very high top speed
Get a gear speed calculator downloaded and have a play with the ratios
IMHO 1st needs to be 40+ 2nd 60+
Diff ratio needs to be low with a very close box and 3.9 is the lowest Sierra easily found
Your power should pull a 3.6 with ease but then gears need to be lower
A bit of a conundrum

ive have a spc semi helical gearset in mine with long first.

i have the same power roughly and with a 8k limit mine does 58mph in first gear, its perfect like that

im running 205 60 r13, forgot diff ratio maybe 3.6

[Edited on 16/7/15 by beaver34]

Not as much power as you but I have the SPC box in mine, it's lovely. Running a 4.3 mazda lsd. 1st is just shy of 50mph.