If you are powered by the original equipment engine a 226 Flatead, it was designed by the best engineers of those times, to run best with those existing gears, the the best other thing to have is a new O/D Saturn (NEW Improved VERSION OF THE Warn O/D)
The 7.50x16 was original equipment in the Military Cerlist diesel powered FCs. These trucks have a lot more torque but were not made to go as fast.
The best tires, my opinion, the FC-170 SRW are the commercial grade bias 8-10 ply 7.00x16, they work the best with the torque and brakes that you have.
9.00x16 will not turn with out hitting the springs, and the overall effect would be that you would go slower, from lack of gearing, the Dodge trucks had 5.13 gears and a 4 speed, you need more engine power, and a clutch disc bigger than you can ever fit.
Sure, I can run an easy sustained 100 mph, run 37" tires, the body has been modified, the front axle is wider, to clear the springs and steering. But most of all, with a very modified high performance 434 cubic inch engine and a 4 speed automatic, but I also run really monster disc brakes to stop it.
900x15 tires are wide and tall, but most of all you only have 11" drum brakes.
: Can anyone speak to alternate tire sizes on a
: FC 170 ?
: I am considering going to 750-16 to increase
: top end by 2 or 3 mph. Also considering
: 900-16 for the same reason, increased mph
: without re-gearing or an overdrive unit.
: Are there fit or safety concerns with either
: of these alternate sizes. Understandably,
: one might not want to exceed 50 mph in a 55
: year old FC 170.
: Thanks, Bill