Update I contacted the guys at supersix motorsports and this is what I found.
Dear Super Six Motorsports
I am interested in your 4.0L SOHC heads. I was wondering if you had any dyno
results yet ? I have a ranger, I am more interested in gaining low RPM
torque then high RPM horsepower.
No, we don't have any dyno test results yet. LowRPM torque versus high RPM
horsepower, then you really don't want full ported heads. What you'd want is
this: ported exhaust bowl and exhaust port, milled .020" to raise
compression, leaving intake port stock and valves stock, but use a fresh
3-angle valve job. If you open the intake side, torque will suffer so you'd
want to leave the intake side alone.
How much would something like that cost and what would be an estimated gain
? Would that require using a higher octane gas ?
$750, yes, you'd need to run premium with the increased compression ratio.