564000
31" is the usual max size.
If you have a YJ your in luck. The leaf spring lift kits are the cheapest. My RANCHO 3.5" kit cost me $336.00 some years ago. I think they're still there about.
If you have a TJ....OUCH! The cheapest lift kit I have seen for a TJ is a 2" kit for $550
But most kits go for $850 - $1050
They really rape you for front coil spring suspensions.