A stock 258 motor (possibly even tired?) will not benefit from a 350cfm carburetor, simply too big. The Carter YF, believe it or not, is a very simple and reliable carburetor! I ran a 1BBL Carter for years on my old '77 258 CJ-7, before I built a high-performance 258, and I simply rebuilt it once (when I first got the Jeep), and never had a problem, ever, not even adjustments.
I sold a Carter YF 1BBL to a guy in California on Ebay, he bought it simply so he could pass emissions, then he put his other carb back on. He had modified his motor, and couldn't pass because of the size of his carb. The trusty Carter YF ran clean and great!
When i finally did my performance 258 for that '77, I had a lumpy cam, performance head-work, dual exhaust headers w/custom 2 1/2" exhaust, aluminum 4BBL intake, and I ran a Holley 390 cfm 4BBL. Even with the performance mods, I have to admit, that carb was too damn big. Even after rejetting it (you can only jet so low before it just won't run right), it still ran so rich, your eyes would burn standing behind it.
It sounds like your problem lies elsewhere. You could have ignition problems under "load", could be starving for fuel (elsewhere than the carb), or a number of other things. If it started after doing the electrical work, tho, that should tell you where to start looking. <img border="0" title="" alt="[Wink]" src="wink.gif" />
Don't condemn that Carter YF, hell they were used all the way back to the damn CJ-2A and if they were that bad, they wouldn't have been carried that long, LOL.