My old B reg, 200 tdi 90 i had had a galvy chassis, i left it and it dulled down nicely on the cross member.The rest you can't really see with a bit of road dirt.
At the most i'd paint the cross member, but i'd rather have the front bumper galved to match!
As for being a target, 90 ARE a target full stop at the mo so i'd protect any 90 / 110 regardless of it's chassis.
P.S best landrover i've ever owned!