Crackling electrical is going to be a short somewhere.
I would say between the Ignition switch and the Coil or Starter.
There is probably a bad wire in the ignition circuit causing either the starter to short, or the coil to fire at the wrong time.
If the engine doesn't "die" right after the key is turned off, the crackle could be part of the system dieseling. The engine gets "quieter" as it is stopping, it hits the next plug and you will here it crackle before it dies completely, this may be due to incorrect timing.
$4500? you can find a fully working 88 for that if you are willing to look around.
To find that crackle, you will need to start / turn off the engine with someone watching for sparks (easier to do in the dark)
most of the time if you can "hear" electricity, you can also see it shorting as well. Watch the starter solenoid, and the coil for the crackle.
You will want to have the timing checked. You didn't say if it was an I6 4.2L or a 4 cylinder.
The 88 4.2L is going to come with a Pukegoat BA10/5 transmission.
This is just my opinion, unless you are very mechanically inclined, I would look for a late 89 or 90 YJ. 4.2L over the 2.5L, and definately AX15 transmission over the Pukegoat BA10/5. I would also suggest getting a later model YJ with Fuel Injection. Carburetors require some tweaking and extra know-how from time to time. If you are going carb'd I would recommend switching out the Carter BBD Pile-o-Scrap for a Motorcraft 2100 or 2150 (there is a guy that makes a kit for the purpose of swapping onto the 4.2L engine on EBay).
late 89 and up will have the AX15 transmission with the 4.2/4.0L, if you go 94 or later, you get the External clutch slave cylinder, of course this assumes you are getting a manual transmission and not an automatic.