Not a 40 series, admitted, but on my 80, I've got 305/70/16s on 10"x16" -20 steels, measuring 33", and I recon they're at the limit of the 1HZ (no turbo) gearing.
Top speed has dropped from 140 kph down to 125-130 kph, and I think bigger than 33" would bring it down more due to the "overdrive" effect.
Looks ok though IMO, and it really is down to personal preference. I like the look of 40s in both scenarios, tall & skinny and fatties.
I've driven both types offroad, and they react differently (depending on conditions) but I can't say one is better or worse than the other, but they are and feel different in many ways when driving.
I like the wide tyres on asphalt though, IMO skinnies dont work well on the black stuff.