For the money youd spend on the head, your not going to gain a lot in return. IE port and polish, get the intake and exhaust manifolds port matched where the openings line up for smooth flowing, no steps or lips. Most of the time they are close, but little things like that dont cost a lot and you can do them.
Gpuller who has posted on here has a 720 diesel, and I built his fuel injection system for his tractor. Maybe he will chime in here and comment on what he thought about it.
I would first check your fuel pressure, see what it running for psi under a load. Lets start there. 30-50 psi under a hard load is good, I have run electric pumps to keep it around 100psi before, but did not see any real gains in that, but it did not stumble either.
Convert your air cleaner to a dry air type. Good clean air with minimal restrictions goes a long way. You should have 13mm pumps in your tractor with 6 hole .010 dia injector tips...that was factory for them. If the pumps are Bosch pumps I can get you bigger barrels and plungers, as well as injectors to help.