Fun Fact: This webpage started cause i did not know how to craft a button :D
Here are some things to note Jumping From Modern Minecraft To b1.7.3:
1. Don't use the vanilla Launcher, Use Either BetaCraft or A .zip mod pack for multiMc based launchers. (beta Unleashed is what i use)
2. Hunger is not a thing, Food Works more like an insta-heal item, This is Overpowered and to balance this, you can't Stack Food
3. You can't Sprint, The fastest way to travel is minecarts
4. Bows are closer to machine guns
5. You can't put 2 chests next to eachother, you need atleast one block between then and one block of air above them. Trapped chests don't exist either, so no using trapped chests to circumvent the first restriction.
6. If you are playing on an M-based Mac Computer, Versions before 1.6 (including b1.7.3) colors will be really messed up (this is refered to as bluecraft) a solution that works for some is forcing your game to fullscreen with cmd+shift+f11 (if you dont have fnlock on (weirdo) you need to press the fn key too)