Harvey London did pass the time by typing:
> Can someone explain why some after market parts for the 4.0 do not include
> the 91 and 92 model years? I have a 92 that has the typical leakey valve
> cover. I decided to replace it with an aluminum cover, but I found most
> catalogs only offer covers for 93-04. After looking at other items there
> were quite a few that also skip the 91-92 years. Some of those parts
> include cap and rotors, spark plug wires, and headers. The thing that I
> find really odd is that I have found some brands that say the same parts
> listed above work for all years 91-04. If there are no differences, why
> would these manufactures and resellers give up sales for those two years?
> So, what are the differences between the 91-92 and the 93-04 4.0 engines?
> Thanks!

They made some engine design changes around that time so it's probably
easier for the vendor to simply not list unless they actually tried
it on an older engine.

Most 93 parts should work but to be certain drop by the dealer and
have them look up the valve cover for your engine and for a 93 4.0.

This site is a good one for chasing down parts.
http://www.chryslerpartsdirect.com/moparonline.htm

--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!