[brric]

Yea if worst thing I need to worry about is being sure to turn off air compressor before I weld I'll be fine with that but don't want to have to worry about nothing else even in future, I found a pretty good deal on some 4/0,4/0,4/0 mammoth triplex underground which is aluminum not copper but it was rated for just over 300amps but in my head I figure with voltage drop that may put it just fine but I'm not sure was wanting someone else's opinion that may could tell me for sure

1. You need 4 conductors.
2. You need a main disconnect at the garage.
3. 4/0 conductors will require reduction or the use of larger ampacity breakers to accommodate their size.

 

[brric]

I also have plenty of room in my main box to put any size of breakers in that's needed

Your main panel probably won't accept a large enough breaker to accommodate 4/0.

 

[brric]

Would taking the diameter of the conductor be an option? Enough to make it fit inside the breaker? They are 19 strands

Breakers are stamped or labeled with the minimum/maximum wire size they will accommodate.