The tonnage, speeds, fuel range, and weaponry of all the TRO 1945 units were based on my research of those units via Wikipedia. I'd recommend checking your base figures there, firstly.
For any weapons not already covered by the TRO, well... I used a pretty basic approach wherein muzzle velocity was used to calculate ranges and damage was... somehow related to a combination of weapon diameter, muzzle velocity, and rate of fire. To avoid making a jumbled mess of the rules, I basically anchored most weapons from cannon size and up to the same range/damage values if they had the same muzzle diameter, so all 20mm fighter cannons had the same stats, as did all tank cannons, and so forth. If any were to have special benefits, I figured quirks could cover the matter.
Of course, that was all a few years back; I'd stopped myself when i began trying to stat naval weaponry, since the project had already gotten bloated enough for a freebie.
- Herb