Converting pre 91 to HO

I've heard that the pre 91 engines (not labeled as high output) can easily be converted to the high output status by changing out some parts. What exactly has to be chnged and what other unforseen mishaps would I run into. Est. Cost?? Has anyone done this who could give me some info. because eventually my cherokees engine will need to be rebuilt! thanks later.
:spam:

It's not as simple as some folks have said; there are a lot of parts to switch over.

You'll need the following (not a comprehensive list, just what I know was changed...)
H.O. Cylinder head.
H.O. Intake manifold.
H.O. Exhaust manifold.
H.O. Computer, wiring harness, & sensors.
H.O. Emissions stuff.

That's all I can think of. Your best bet would be to buy a whole donor XJ and swap all the parts you'll need from there. It'd be cheaper, and you can map out the original connections as you strip it.

Mostly it's all from the head up. You can still use the renix harness and computer if you stay with the 91 - 95 h.o. set up. Also if you keep the renix set up you have to use the renix flywheel. Do some good internet searching there is tons of information out there for this. Showing all the modifacations that need to be done. Like the new tranny and accelerator cables. I'll start you out in your search with some information that I have not seen in any post the down pipe is different depending on the exhaust manifold you use.


Also just my $.02 If you are looking at going with the rebuilding your own or haveing rebuilt there is only about a $300-500 difference in doing a stroker which will give you even more power.