This is what mine looks like, externally now (albeit ARES, not SRC):
Internally, it has an Element silent piston head, SHS 12+3steel tooth piston, M100 spring, Kings Arms tappet plate and dream army air nozzle.
You could still upgrade further- but if it's a Version 3 gearbox- it's generally pretty awesome! have an SRC MG36 too good fun
You will like the gun!