Great job Allan. I've built all of the 1/72 scale Abrams kits (including the Italeri reissue Esci kit) and hand down the Revell of Germany kit is the tops. Add the ExtraTech PE set and it is superb. The old Esci M1A1 is not worth finding unless you collect Abrams kits like I do.
The old Esci M1A1 includes the 120mm instead of the 105mm main gun, as well as an incorrect bustle rack/grunt rails. I think the Esci (now Italeri) M1 is the best straight M1 available (when compared to the Hasegawa and Matchbox offerings). The old Esci M1A1 turret has some dimensional issues since they just do a mold swap and only change the gun tube and add a bustle rack. No modification to the hull sponson box to add the NBC system or armor changes to the front slopes of the turret. I don't recall if they add the longer turret sponson boxes or not. I also believe they retain the M1 style blow off panels.
The older style T-156 tracks are just fine for an M1A1. Even though all M1A1HA and M1A2s have the newer T-158 tracks, there are still M1A1 tanks with the older style tracks, believe me, I have a few myself. Besides, most tanks during Desert Storm still used the older style tracks.