I'm running 37's with 5.11 gears. I like where my gears and tires, etc, are…just looking for some possibly easy ways to give it a little more zip. Nothing major….way too deep into this jeep already!
With my CJ7, I tried it all....
I bought it with a tired (165K mi.) stock 258, BBD carburetor, CA emissions engine, 3.31 gears, T5 5-speed, and 32" tires.
I tried the nutter bypass on the ignition, and didn't notice any difference.
I switched to 4.10 gears, and obviously that made a difference... but you're happy with your gears, so that's a moot point.
I installed the Mopar MPI kit (and a new timing chain), and the driveability improved tremendously! But... not much noticeable difference in power.
I added a throttle-body spacer (which we all know is bunk), and it made no difference at all.
I rebuilt the engine, and added a Borla header. It sounded great! I really wanted to notice a difference... but it wasn't there.
Then, I installed a 4.0HO head... and it was amazing!
I never put it on a dyno, but the seat of my pants told me it was a good 25% power increase in the rpm range I was using. That engine pulled strong from 600-2500rpm!
I used to tell people that I was getting V8 power from my straight six... and I believed it!
HOWEVER, now I'm driving a CJ8 with an old, tired, carbureted 350 small block... and it would run circles around my previous 258 CJ7!
I took a ride in Randyzzz 5.3 Scrambler, and it's even better!
Sorry for rambling on...
To summarize, the best bang for your buck with the 258 is to add a 4.0HO head... but for similar cost and effort, you could swap in another 100 cubic inches (350 SBC), and be REALLY happy with the result.
There's no replacement for displacement....