DSA is going to be just about the standard against which all others are judged. Pricey, but almost certainly worth it. They'll make 'most any combination you want and make sure it works, too.
There have been a number of companies and small makers who've built parts kit guns over the years. Unless you know how to evaluate one, I'd probably avoid them.
The Stg.58 is nice, though heavy. (Well, they're all heavy.
) Cool integral bi-pod, metal handguards, cool flash suppressor. Other kits have their merits as well -- what do you want?
I like the Israeli version, but if I was really looking to buy I'd probably get a para. FALs aren't really match accurate under the best of conditions, though plenty accurate for a battle rifle. From that point of view, and seeing as you have an M1A loaded, a Para would make a really handy, compact companion.