from easy to hard,
number one/1. you will need a texture pack
number two/2. you will need a map that consists of basically plains in middle and generally covers hole map till edges which is hills and protected ( basically make a generator )
number three/3. you will need a order system
number four/4. you will now get into further detail and add client mods, this will be hard but if pulled of this will be the best fallout server because i havent seen an realy fallout server yet
1.you will need to make a mod that makes the following cretures different form
-skeleton/ will be a ghoul
-zombie/ feral ghoul
-spider/ rad scorpion
-cave spider/ albino rad scorpion
-human waist lander
-ghast/ eye bot
-enderman/ nightkin or stealth supermutant
-chiken/ chicken
-cow/ brahmin
-creeper/ centaur
-sheep/ sheep
-pig/ pig
-silver fish/ silver fish
-slime/ slime
-wolf/ dog
2. then you will need to make seperate mobs
-death-claw
-robots
- raiders
-waislanders that trade
-mole rat
-yao gwai
-enclave
-BoS (brother hood of steel)
some more if you like....
.i was going to do this but lack of funding lead me to stop server, and the fact that minecraft soon lost its edge
if someone does this, i will play again

Additional Notes

how to make a fallout server.