Since you say the bottom end is in good shape, it would make good sense to focus on the cylinder head.
The stock style Hughes valves and 340 valve springs, pay for good multi angle valve seat work would be a start.
Shave the head to get the compression up into the low nines, that is a bit conservative, but you say you are not a tuner..
cc your heads use the formula .0069 to 1cc ,measure the existing piston recession and with an on line compression calculator you will know exactly what to tell the MS to mill off the head.
Talk to Oregon Cams, tell them what you want for performance and the specifics the engine, Tom will recommend a cam.
What are your plans for an intake-exhaust-ignition ?
