Unfortunately this is not compatible with the Galil Ace.
To answer my own question and other people's, yes this will work in a galil ace ak. I did it with mine, had to grind some parts and remove the left side safety switch to get it to seat properly. It runs flawlessly, I've had zero problems.
Yes this will work in a Galil Ace, I have it in mine, but you have to do some machining to get it to sit properly and the safety on the left side has to be removed. I cut the polymer magwell and attached a 100 rd drum. It ran flawlessly, it took 8 seconds to empty. If you don't mind the left side safety being removed then I highly recommend.