Mike,
If memory serves, 298mm will work for 36o/3x, NR hubs with Araya alloy rims, but I always measure everything manually (old hobbit..:).
Guage? If you weigh 175# or above: use 14 on the rear; 15 should be just fine on the front, but fit is important on the old hubs as I have seen considerable differences in drillings! If your riding style is smooth, etc., 15ga all around will work. I am also talking about modern spokes, i.e., DT.
Chuck Brooks
(the BMX wheel awaits, as does the owner!!)
Malta, NY