tyre sizes question

hello

iam needing to change my tyres soon
i have a disco 3.9 v8 p reg (1997)
iam new to this (would this be 300 series????)
ive got 225/75R16 at the moment ive been looking at the newer discos
and i notice that they are 255/65r16 could i fit these to my rims ?

or which tyre size could anyone recommend for road use
iam not looking to do any alterations to my arches
iam hoping to go a little wider


thanks in advance
garry