I am guessing you are after a triple? I don’t think the M8000 comes in triple, single or double only and if you have an old 3 ring front mech it won’t really be right for the 2 ring setup.
I would either look for an older XT M770 9 speed triple set up as this will give you the 44-32-22 rings or the 10 speed triple will be 42-32-24. Another option is the XTR M980 on sale at planet x which again is 10 speed ratios but closer than the typical 11 speed ones.
I am assuming that the chainring spacing on 8 speed is the same as the others. I have intermixed 9 and 10 speed with no problem as they are the same spacing and the chain works fine (use the chain specific to the cassette) but not 8 speed as that is before my time.