are we talking tyres here, or tiers
you need to tell him if your going rigid or staying with the shocks! that's for the gap/mounting required.
you do know you can buy off the shelf mudguards and cut them to fit yourself? ( I figure that is what he'll do anyways) the tyre is for getting the radial gap right as there are different size wheels!!
@paulwhite, whats a stile? (apart from a device for getting a person through a field boundary)