Just bought another Ranger, it's a 1999 Super Cab 4.0l, Auto Trans, 4x4. Well its like my other 99 Ranger and has head problems. I used 97 heads on my other Ranger and it runs fine. Would just like to fine some new aftermarket heads to put on this one. Has anyone on here used ITM heads? Thanks for any help. CharlieK

 

The 1998-2000 heads have smaller exhaust ports to increase the velocity of the exhaust to get Cats hotter faster to pass stricter cold start emissions, and exhaust manifolds to match
So not a good idea to use earlier heads unless you change exhaust manifolds as well.

"It works" is not the issue, of course "it works", lol, its the long term effect that can heat up the exhaust valves on earlier heads causing burnt valves, but may never happen, totally users choice.

Morana Racing has heavy duty 4.0l ohv head sets for $480, bare bones: Tom Morana Racing Engines

ITM heads should be as good as any others

The 4.0l heads have a thin metal area between valve seats so will crack there if over heated, it is just the way the casting has to be, so there are no "no crack" 4.0l OHV heads
Not sure what "heavy duty" means but it would not have to do with that area of the head
Morana says their castings have thicker port metal so can be fully ported for intake and exhaust, maybe thats what it means