Volvo F7 GVW?

The plate you photographed is for the cab only - volvo used to number every cab, each with it's own spec. There will be a chassis plate somewhere else in the cab which will have the GVM on it. The F7 was made with either 6.5 tonne or 7.5tonne but the heavier option may not have been available in USA. If you contact Volvo HQ in USA they should have a record of the original build specification.
To look at spec sheets go to www.hunteroldtrucks.com and click on Volvo heritage group page

apart from filling the tyres with helium theres not much you can do ..unless its possible to get the truck gvm engineered upwards? or a permit ...or as the other guys say a 3 axle truck (the added braking capacity of the extra axle is always a bonus ! )

Common sense be darned, and all reasoning aside, I will be getting the Volvo tomorrow!! I'll have an update shortly...