OK, Well I'll just go against the grain and say, since your engine is rotating, power anything that rotates off that, via belts etc. You can shield/guard the belts, or just use the safety feature between your ears and not put yourself in harms way.
Next best/safest source is pnumatic/compressed air.
Depending what engine you get, you could pull the injector/pump to one cylinder and run that as a compressor - alternatively you can probaby pick up a belt-drive compressor head cheaply as they seem to be everywhere now.
There is a disadvantage in double or triple converting energy. For example an engine, reciprocating motion, giving rotation, to generate electricity, to rotate a motor, to drive a piston compressor (reciprocating again!)... Waste/conversion loss at every step.
If you can find an old Miller "roughneck" weld/genhead, that takes care of those two things in one go.
The advantage with pnuematic tools is that they'll generally be field servicable. If a rotor or stator burns out, it's a trip to town to order a part to wait a month...