the 3.4 does not have more power......they are harder to find in good running condition....are more expensive to buy and work on....the only major performance upgrade is to drop 3 grand on the supercharger.......however the 4.0 has same hp, but more torque.....easier to find....cheaper to buy in working order, and cheaper to upgrade and work on.....easily stroked to 4.7L,  there are tons of more performance parts....and then after that there still is the option of supercharging........but anyways......i think hes gonna run the stock 4.0 for a whille with the jeep clutch bellhousing and tranny, use the r150f tailhousing, and toy tcase, solid axle the front and throw some 5" springs out back......then later on stroke it, gear drive tcase with 4.7 low range........and after all hell have enough power for anything, and if he needs more its easily obtained.....enough gear for crawling, and enough dependability to blast through any mud, up any hillclimbs, jump the dunes, and still drive home w/o having to worry about a friggin head gasket like with the 3.0......either way theres a lot of      and    to come so itll be awesome