There are a lot of companies that do AM for Abrams exteriors; Verlinden, Voyager, Lion Roar, Legend, etc. The only interior set is the old Verlinden set. It is pretty bad and not close to reality.
I have built 3 full interior Abrams. For mine, I started with partial interiors from the old Dragon Abrams kits. They included a pretty nice driver's area and upper turret. I scratch built the lower turret baskets. The kits can still be found on eBay for a relatively good price. You can probably get a few of the interior sprues if you ask around on the forums too. Many people dindn't use the interiors.
Most of the gray parts are from the Dragon M1A1 kits.
Hereare a few more examples:
CMK does a full engine and compartment too.
Legend does a couple nice TUSK sets for a modern tank in Iraq over the last few years. Voyager has a good USMC A'stan Hog set too for an up to date model.
Perfect Scale Modelbau (PSM) just came out with a couple good USMC conversion sets too.
AFV Club, Trumpeter, and Bronco all do track sets as well.
If you narrow down when/what type of Abrams you want to build, we can direct yo to the best kits and AM sets for it.