A BSG: 2003 Galactica using the GURPS Traveller: Interstellar Wars ship design of 1 dton = 500 cubic feet a Jupiter-Class Battlestar (Galactica's class) at 4720 ft in length, 1762 ft in width, and 602 ft in depth has a volume of 5,006,617,280 cf. This makes the Galactica a 10,013,234.56 dton Dreadnaught.
The Mercury-Class Pegasus is 5872 L x 1762 W x 602 D comes to 6,228,571,328 cf in volume or 12,457,142.656 dtons.
A Valkyrie type Battlestar would be somewhere between the Galactica and the Pegasus in size so I would build it on the average of the two other classes. I would say that a Valkyrie type Battlestar could be built on a 11,235,188.608 dton hull.
As for armaments the heavy KEW weapons if built in GT: IW could be replaced by Fusion Gun bays, the missile launchers could be replaced with either heavy or light missile bays remembering that the Valkyrie type Battlestar uses more missiles than the other two classes. The light KEW weapons could be replaced with either dual Fusion Gun heavy turrets or triple Laser Cannon turrets for point defense. The Battlestar doesn't mount a spinal mount weapon.
Small Craft squadrons would be four light fighter squadrons for the Galactica type Battlestars, two for the Valkyrie type, and eight for the Pegasus type. There is one squadron each of the Raptor multipurpose shuttle (could use a 30 dton ships boat) for the Valkyrie and Galactica type Battlestars and perhaps twice to three times that for the Pegasus type Battlestars. Now the Galactica and the Pegasus carried a shuttle that is likely similar to the 100 dton interplanetary shuttle as to the number this is unknown and it is also unknown as to whether or not the Valkyrie type carried any shuttles. The Shuttles were used similar to the US Navy's C2 cargo planes. While Raptors function as a cross between a AH1N Helicopter Gunship, SH60 Seahawk ASW/ Transport Helicopter, and an E-2 Hawkeye AWACS plane. Now Colonial shuttles and the Raptor are FTL capable, but only the Shuttle in Traveler could be built to use a Jump Drive. Since most all ship to ship combat in Traveller takes place in normal space the Raptor being used as a recon scout won't need a Jump Drive as they would just be launched after entering a star system to see what's there. A BSG Traveller campaign would have to forget the instantaneous FTL jumps of the BSG:2003 wouldn't fit Traveller.
Though in the series the Galactica began with just a token platoon of Marines as it's Ship's Troops Detachment in a scenario where it is fully manned the Galactica could easily man a full Battalion strength Marine Ship's Troops Detachment similar to a USMC Marine Expeditionary Unit. The same goes for the other two classes of Battlestars.