A 426 Hemi would indeed be something awesome but finding one or trying to get someone off of a 426 is like trying to pull a tooth from a lion.
A 427 would be just as cool but again also hard to find or get ahold of.
I understand why some people would think a bb in a jeep is a bit extreme... but it is very rare, It would surely set it apart.
I don't mean to say I would never use it, just not to the extreme. Not unless I change my axles to handle it. (which I might :-P)
As for only 5% noticing the differance between a sbc and a bbc, I would have to wonder about that. The sure size differance is staggering. A sbc in a yj leaves alot of room as a bbc would fill the engine bay but still fit nicely, even though I would have to change spark plugs through the front wheel wells LOL Oh and not let us forget the sound of a rat engine is profound and unique just as a Harley Davidson. Just cant mistaken it!
My original plan was BB and steered away from it cause many said it wasnt practical for the weight factor alone, I have felt a bit empty since. I feel its like many things in life we seem to just not do because of some reason or another, but then we go through life saying or wondering "What If?" I remember as a kid sitting back watching friends taking a jump off a local hill that was 20 some feet above the water and didnt try it because it didnt seem safe and others saying it wasnt practical. Then when I turned 25 I got the guts to take the plunge and after I thought of all the time I had robbed myself of the fun and thrill of doing this. I just feel this is another one of those times. Just think about it for a moment, what would turn your head quicker a Jeep lifted as high as mine with 35" to 37" tires with all the goodies, which we see all the time and have become use too seeing even alot with v8's OR! one with all that and the profound one of a kind rumble that a bbc makes, I dont know about you but I think my heart would skip a beat. It would be like Jessica Alba walking into a room your in, YOUR JUST GOING TO NOTICE!