The original optional 15" tires on '54 1/2 ton trucks were a little larger diameter than the stock 16" tires.

The Toyo radials I have on original 15" rims on my pickup are as big or a little bigger diameter than the 16" Cooper radials on 650x16" rims on my suburban.

Both my trucks steer and track as nice or better with the 6-ply truck radials (properly inflated at 40-45 psi) than with 650x16" bias tires.

Tim