I am getting ready start a build on a truck that will be my daily driver & hunting and camping rig as well.  My tire size I plan on running are 35s or 37s.  The motor is going to be a beefed up cummins (400-450hp).  I am not sure what gear set to run with.  I want it to have power but not unbearable to drive daily due to fuel mileage.  I am thinking that 4.56s is what I want but that seems pretty low.

Also, I want to remove the chain driven NP241 that the truck currently has and go with something a little bit stronger transfer case.  I was thinking about running a NP205 or maybe a Dana 300, but do not know which one is best for me.  

Any help on either issue would be great.  

4.88s would be better off. especially with 37s. the 241 atually has a lower gear set than your 205. stay with the 241 and take care of it properly. changing the fluids every 15k  

If you are running a CTD, I would tend to lean toward a 4.56 here over a 4.88 because of engines very limited RPM range. I also would not consider a 4.10 a option here.  On Tcase, a CTD comes with a 241HD and I would place it above a D300 in strength. I would not bother with a swap to a 205 as 241HD will hold up fine if you keep oil fresh in it as mentioned above. The links have very small bearing surfaces in chain and they will suffer and wear out sooner if oil is not keep clean and fresh.