Do any of you know if headers from a 90-97 4.0 ranger fit on 98-2000 4.0 rangers? I have a 2000 4.0 4x4 ranger and adding headers to it while I replace the heads. Do any of you know why headers for the earlier model 90-97 4.0 Rangers won't fit the 98-2000 rangers? I found some decent mid length headers supposedly for 95-97 model's and I'm wondering if they will fit on my 2000 and if not, why exactly won't they fit?

 

I'm thinking they won't fit.

98 was the first year of the 3rd generation Ranger.
Going from Twin I Beam suspension to the Short/Long arm suspension, so the inside of the engine compartment is also different.
And from a steering gear box to Rack and Pinion.

 

No
The 1998-2000 4.0l OHV had a new head design with smaller exhaust ports to increase the velocity of exhaust to heat up the Cats faster, emissions thing
So you would lose power with the older style headers, even if they did fit, might even cause burnt exhaust valves

Exhaust manifolds(headers) are designed to LOWER the pressure at the exhaust ports at a specific RPM
Ranger Factory exhaust manifolds are Tuned for mid RPM as lowest pressure, thats about 2,500rpm on the 4.0l OHV
After market headers are designed to lower that RPM band down a bit, to say 2,100rpm for lowest pressure, so more "low-end" power, but you lose the mid band power
But there are also "racing" headers that raise when lowest pressure happens, to say 3,100rpms

The design for headers is complicated, above my pay grade, lol, but an interesting subject

The Lower pressure PULLS exhaust from the engine, leaving more power on the crank for the rear wheels, its called Scavenged power because its FREE POWER
But it is strictly RPM related as far as the design, low, mid or high RPM, pick one, lol

Automakers have been using TUNED scavenged power since the 1950's in exhaust manifold design
This is where the MYTH of engine's needing back pressure came from
People would install "free flow" headers, not designed, just larger pipes
Then go for a drive
"WTF!!!, I LOST POWER????!!!!"
"This engine must need back pressure"
No, no 4-stroke engine needs back pressure, try a potato in the tail pipe, lol
They lost power because they took off the factory TUNED exhaust and put on an un-tuned exhaust, so lost the scavenged power