Iv'e been running LPG on the 4lt Mopar for 3 years with no issues. As long as you run a valve saver and run the thing on petrol every now and then it's not a problem.
Up to 164 k right now and the only thing I'm doing with my motor is (still) replacing the welsh plugs.
LPG is actually kinder on motors with cooler input fuel, less injector wear, lower carbon build up and lower price.
Downside is the lower power....about 10%
As my sig says - my Jeep has Gas. All three of them..Grand, Full Size and the CJ10.