"4wd.com had an 1994 LS1 engine in a 1989 YJ featured in one of their catalogues"
not to nit-pick....but the LSx line of engines didn't exist in production lines untill 1997..when it became available in the corvette.
the LSx engines make gobbs of power, and are very reliable. for minimal money you can put a cam in a base lsx engine and make 400+ hp with a nice flat torque curve all the way up to 5500rpms.
however, for an offroad vehicle, the TPI motors are hard to beat for low end torque. in stock form the measly 305TPI motors were putting out 300# of torque at something like 2800rpm.
i've seen some mild built 350s and even some 383s put out 450# torque at the wheels and all before it hits 3500rpms(on a dyno in a camaro/firebird drivetrain). that TPI system is just a torque building monster, and at low rpms. would make for an insane trail truck, and be fairly inexpensive to build.
than again you can get some 382ci LSx short blocks for under $5K...mild heads, nice cam...and you'll have 550hp at the crank, with probably 500#+ of torque, along with better tuning capabilities, and better efficiency.
i'm sure it's not a huge concern, but the LSx motors get fantastic gas efficiency. my poorly tuned LS1..with a decent size cam...gets 25mpg highway, and puts out a conservative 450hp at the crank.
