what are you working with, i.e. tell us what specific machine gun you intend to mount?
This is open ended at the moment. The browning 1919 looks like a good starting point for discussion.
belt-fed?
Most likely, but again, open ended.
how much ammo do you need to carry?
Good question
do you have a large ammo can?
Got a bunch of 'em
how close does it need to be to your machine gun?
Close enough to reload on the spot
feed chute?
Probably not
do you have any external power requirements, e.g. solenoids, motor for your ammo feeding system?
I'd like to keep it a simple as possible, so no, probably not. C'mon, they have 'em in Africa and the Middle East in horrible conditions with less resources.