You make this sound like it's a test question.
36" is w a a a y too long if you're going in one face -- and plunging out the back side. "and going out the back"
600 kCMIL is brutally stiff -- even in aluminum -- so I could never recommend going with 8" as a depth.
You are not providing ANY of the circumstances that would dominate my own can sizing -- which is never predicated upon the NEC minimums. (I never, ever, attempt to squeeze (feeder) conductors into spaces so tight.)
Lowest cost means that the actual installation goes off without a hitch. That will not happen with NEC minimums. Tight space takes extra time... sometimes amazing amounts of extra time.
The NEC permits 9 #12 THHN in 1/2" EMT. Only a fool would design to such a scheme. Five #12 is the maximum that one would want to run in 1/2" EMT. Nine #12 -- going through four full nineties -- may require use of a power tugger. Yes, it can get that bad. Pulls like that cause the back injuries so common to electricians.
