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I did some research at the local library reference section. They have the Chilton 1993-96 light truck repair manual and under general engine specifications it lists an H code and an R code for the 5.8L engine.
I recently purchased a core 1994 5.8L engine (for the roller cam feature) and am curious which version I have. The decal on the valve cover has weathered to the point of illegibility, although the bar code is still clear. The motor is from an F150 4x4, probably Canadian built, since that's where the truck was.
I misplaced the notes I made, but I recall one of the code engines made a bit more power than the other.
I am also curious if this engine will have more noticeable power than the worn out 1969 351W-2V it will replace in my 1964 Fairlane. I will just use the newer engine as a long block and so reuse all my old parts like induction, exhaust (long tube headers and dual exhaust), oil pan, etc. I don't rev it over 4000.
The R code longblock 5.8's were in the 93-95 Lightnings: 65mm throttle body, GT-40 intakes and heads, different cam profile and dished hypereutectic pistons.