STAR WARS SOURCEBOOK SHIP STATS
The first WEG publication where we see large capital class starships is in the Sourcebook, and in that book, there is a note that some of the stats for those vessels is missing. Namely, the Shields and Hull values. An explanation is given that the GM is intended to use these huge destructive vessels for dramatic effect. Players will be using starfighters and small craft no bigger than the Millennium Falcon .
Well, WEG changed its mind on this (what if a GM wants to run a battle between Rebel captial ships and the Imperial Fleet?) probably before the ink dried on the Sourcebook, because, all other sources include full stats.
The missing stats for the ships in the Sourcebook are all listed on page 50 of the Rules Companion. And, that book includes a combat system for Capital Class starships, too.