Well 6 days in and the aro's appear to be tolerating eachother. Day 2 there was some aggresion between the 2 larger fish, but that has stopped. I have the tank divided untill the arow's are at least the size of the gar.
I am inclined to say that this will work out, as the gar rarely shows any aggresion, and i had it housed with a black aro. for 5 months prior to this. Never had a problem between those 2 fish.