i have no self experience with the giant snakehead do to them being illegal in my area, but i do know a good deal about them, just a very brief explantion on them-
they grow big!- 4'+
they grow fast- like weeds
they are very agro fish and do not do well with tankmates, they devour most anyfish they can fit in there mouths, i saw a 11" Giant eat an 8" catfish. your tank is large but not large enough to keep adult for there entire lives, but at least for a good deal into there sub adult stage, i'd recommend to keep them as a soliatry speciemen rather than with anything else