That doesn't sound typical to me. All of the DSA STG-58's that I've heard of had pristine bores. I'm not sure what was going on with that one. The STG-58 kits that DSA has are like new, for the most part. I can sympathize, I would definitely feel reluctant about paying $900 for a rifle where the bore looked slightly pitted.
Call DSA. They have very, very good customer service. Tell them what you want to do and what you saw in that rifle. See what they say. I'm sure they will be honest with you. You can order one from DSA and wait 2 months or so, or.......
You can get all the parts together: Imbel kit, Imbel receiver, FSE and Penguin American parts for compliance, and send it off to Mark/Gumplummer at ARS or AZEX Arms, both in Arizona, and get a beautiful rifle assembled and finished by one of those guys. You will be creaming your pants when you get your rifle back from one of those guys, same as DSA. They assemble very fine rifles, only to the strictest of tolerances and will notify you if anything is out of spec in your parts that you supplied. They can tune triggers (as much as can be done on a FAL), shorten the barrel to a carbine (included in the cost of the build), anything. But then again, there just is something about DSA.....
Many people will tell you that you can build your own, which is entirely true given enough time and effort on your part, but it sounds like you want something a cut above everything else.
www.dsarms.com
www.arizonaresponsesystems.com
I don't remember AZEX (Arizona Expert Arms) website, but you can find it by searching google or
www.falfiles.com .
Whatever you do from these options, you'll love the rifle you get.