As Kenny said, there should be four more numbers prior to this IF it is a Kaiser-Jeep, General Products, or AM General truck. However, 31098 would be right for a 1953 Studebaker-built truck....if you think its a Studebaker, then more information is needed to confirm this.
FWIW, the next issue of Military Vehicle Magazine should have an item in it detailing the meaning and dates of the various serial numbers assigned to M35A2 trucks.
Hope this helps,
David