2003 Ranger would have the 4.0l SOHC engine, 2000 and older Ranger had the 4.0l OHV engine
No lifters or push rods on SOHC or DOHC engines, OHV engines have those.
Never heard of any issue with oil flow in the SOHC engine, or the OHV for that matter.
The timing chain issue was a design issue, not an oil issue.
So you pulled out the engine and replaced all the chains, cassettes and tensioners.
Not sure what it could be, I guess you will need to pull valve cover(s) again and see if anything is loose.