Seeing as it's a work vehicle, you'll save money by staying with the stock flow rate. "Lucky" for you, the 4.0 heads don't flow as well as the stock engine could utilize, so going to 4.6/4.7 with a stock head won't get you the full 18% increase in performance, and therefore demand for fuel, that the increase in displacement would otherwise warrant.
For conversation purposes, let's call it 10% increase in potential power w/ a stock head. Once up to speed and the ECM registers it as "cruising", the O2 sensor will be used to richen the mixture to account for the change. Outside of that "cruising" mode, the ECM won't know any better and will give it exactly the same amount of fuel it is now, saving you money. You give up 10% performance, but being a work vehicle...
I don't know if I'd call it sarcasm, but definitely a certain amount of "knife in my temple" twitch in saying the above. It is completely counter to my gear-head ways. I half became physically ill even typing such words. But the facts aren't wrong. I could make the argument for swapping in a worked over 4-banger to save yourself even more money. But, back to reality...
The Jeep 4.0 is as the reliable beast partially because of it's Rod Ratio, the ratio of the length of the Rod to the stroke of the Crankshaft. On a stock 4.0, it's 6.123"/3.413", or 1.794. According to the post linked to below, Rod Ratios between 1.65 and 1.80 are best, with 1.50 being minimum. With the 4.2 crank and 4.0 rods, it's 6.123"/3.895", or 1.592. Better than the stock 4.2 ratio of 1.508, for perspective. (Source & a lot of other good info:
https://www.jeepforum.com/forum/f176/stroker-regrets-997768/#post9154151)
Add the additional wear-and-tear for the 18% more power, oh wait, you didn't get any more power because you're running the same fuel injectors, but anyways...
Seriously, more power equals more wear on the rod and main bearings, cylinder walls, piston skirts, etc. Long story short, If you're trying to get another 300k, building a stroker is not helpful... Don't get my wrong, we're all in the same boat w/ it costing not much more for a stroker. It's everything else that goes with it that "adds up"...
If I were in your shoes, and even in mine, I would get in contact with Russ P. and make sure that I wasn't painting myself into a corner. SCR, DCR, quench, the list goes on. A few extra $$ spent up front for the right pistons, or camshaft, or ... could save you big $$$$$$ down the road. For a work vehicle, the last thing I'd want is a poorly running, pinging POS that required premium gas. At least yours won't use as much since you'll have undersized injectors... Last time, I swear...
