Good Luck, all your going to get is a website showing a diagram that makes very little sense. Im going thru the same thing. I have an 89 YJ that I just finished the Nutter Bypass on and now Im trying to get the carb and vacuum lines all hooked up again. This thing was a real piece of work when I bought it. Then your going to find out that the stock 258 Carter carb is a piece of #*$&. Its like one thing after another. I dont know about you, but I wish someone would publish a manual,,,,,step 1, step 2, kinda like a flow chart, if it looks like this, go to B, if it looks like this go to step C, if not, go to D etc, etc, Not all engines are alike or have the same crap missing. Its alot of fun playing with though so hang in there and dont give up.
Here is the website. Before I converted to the Howell TBI, this site is the best site to help you unwind the vacuum hoses. No one ever said the vacuum/emission system on the 4.2 liter was simple. The Chilton manual has a good trouble shooting guide, too(taken from the shop manual).
There are some subtle differences (errors?) when comparing the diagram on this site to my shop manuals, but I finally convinced myself the diagram here was correct.
It took me a couple of hours when I did it on my 1990, but when it was done, it all worked great. I had to replace a couple of the vacuum switches on the firewall but when you have it hooked up right it actually does work.
That said, a fuel injection conversion is the way to go. You get to take all the vacuum lines, switches, etc. and throw them out except for the canister/fuel tank lines and of course the EGR lines. Howell, Holley, CustomEFI.com, MOPAR, all are great options. I went with the Howell system and then I custom tuned a chip and it all works great.