The federal Interstate limits are 80,000 pounds gross, 20,000 pounds on a single axle and 34,000 pounds on a tandem axle group, with the federal bridge formula limiting how weight can be spread across axle groups. States set their own limits on other roads and issue the permits.
A load can be overweight without being oversize, and the reverse. Permits are often written together as OS/OW. Overweight permits are tied to the axle configuration of the truck and trailer you list, so a changed axle spacing means a changed permit.
Regulation: 23 CFR 658.17.