Right now 3.8 wranglers are amazingly plentiful and cheap .
As bad as it is , a ton of 3.8 engines were marketed in several Chrysler/Dodge platforms and had a long production run , the Caravan being the front-runner in my mind .
I drove a hopped up 3.8 regeared 4 door , it was actually pretty fun , but so is a moped til your friends see you .
The 3.6 is a good engine , and the newer 8 speed transmission makes it far better is the report ,as a V6 has a peaky power curve.
A TJ is a solid ,solid vehicle - you just have to realize it's a lot older , and naturally is going to need some care and maintenance.
My biggest thought is avoid a beat up , hopped up , TJ , JK or anything that has been rode hard and put up wet - they will eat your bank account up trying to make them enjoyable and reliable again.