can the HMMWV amg242 t-case be modified to have the 2hi option??  

the t-case came with the 6.5td and 4l80e I got to put in my 75 jimmy project.  I would like to be able to unlock the front hubs..  I like the idea of having a full time 4wd option and this t-case is pretty beefy!!  

It can be done but why? The Tcases torque capacity will be about cut in half in 2wd. Personally I lived with a fulltime Tcase for over 20 years with a 79 Jeep J20 P/U and the benefits outweighed the drawbacks. Loose the hubs and run it like it was meant to be run. I found that I very rarely ever needed to lock my tcase diff out even in nasty conditions.  

ya but I will be pushing around a big 60, ya think I'll be loosing a couple mpg's with that beast out front?  or will the diesel just ignore it?  

With a lift and big tires, the extra drag from full time 4x4 will be a much smaller piece of the pie vs a stock 4x4 model with stock smooth tires that has lower rolling resistance so the extra drag is a bigger piece of pie. That being said, it might cost your setup 5% MPG if that and you will love the way it handles and drive with fulltime. I would let it be. I would suggest maybe using 75w90 in both front and rear drive axles to limit power loss. (with fulltime, every little bit helps)  

Good point!!  and I do like how it handles with the 203 t-case in there now... I just need to locate one those rare ford 60's from a 78-79 truck!!