I am literally a step ahead of you on this. Just did it.
Don't go to EFI until your cam is broken in! Get your new engine in, break in the cam, THEN go to EFI. If your engine is not running great for cam break in you can torch your motor right off the bat. It really sucks trying to work out EFI bugs on a motor that is not ready yet.
Full Size Jeeper did EFI install during engine build with success (http://www.ifsja.org/forums/vb/showthread.php?t=183237
) and honestly he would probably disagree with me but this is one of the biggest lessons learned in my build (link in my signature). Full Size Jeeper had some help from folks that have used/tuned a Sniper in the past. SC/397 does carb before EFI too and you would be hard pressed to find someone on this forum that thinks SC/397's advice/work is not top notch. (http://www.ifsja.org/forums/vb/showthread.php?t=186633
There are quite a few Throttle Body Injection systems out there. Summit has like 10 of them, alone. None are tailored to AMC V8 but almost all will work fine. Howell has a system tailored to AMC V8 that is basically a re-packaged, and tuned GM system. All these systems have pros and cons. The ones you see the most on this forum are FiTech, Sniper, Howell, and DIY systems like mine or Megasquirt. Again, pros and cons to each so you can't really say one is better than the other.