I did a model of the Battlestar (and some Vipers) based on Raph McQuarrie's pre-production designs. It has not been said (in any book or production) that they were what the craft "originally" looked like earlier in the timeline, but some of the paintings of Ralph McQuarrie did show up as set dressing making you wonder if the Battlestars did resemble his paintings at an earlier time.
The renderings can be found at:
https://www.battlestarpegasus.com/gal...in/index3.html
I like to think the earlier McQuarrie Viper designs are the ones maybe flown by Adama and Tigh in the earlier days when "the ships weren't quite so fancy, but they gave them a good run." (at least I think that's what Tigh said)