If you want to recapture the early days of Minecraft, then a mod called SSP is one of the best ways to do that. Instead of removing new mobs and items from the game, SSP simply re-introduces singleplayer mode.
Why would a mod do that? Well, prior to 1.3.2, many Minecraft players only played singleplayer mode because it provided the fastest and smoothest gameplay. After 1.3.2, these players were restricted to playing on local servers. Local servers might seem like the exact same thing as singleplayer mode in terms of gameplay, but the game processes local servers much differently than it processed singleplayer mode.
The result is that Minecraft players on older rigs started to complain about the smoothness of the game after the 1.3.2 patch. And SSP seeks to help these players out by unlocking singleplayer mode once more.
Players can still access new Minecraft features like commands and LAN multiplayer. And players who want to switch between local servers and singleplayer mode by default can simply click a button to play default mode with a local server.
Since most mods have been upgraded to local server mode, you’ll want to switch to that mode any time you want to play your mods. Without local server mode, most of your mods will be incompatible with single player.
If you miss the days of smooth framerates and seamless gameplay, then SSP will give your computer a boost. Just don’t expect to see features from the early days of Minecraft return.
How to install SSP for Minecraft 1.6.4/1.7.2/1.7.4/1.7.5
Step 1) Download SSP from this forum thread
Step 2) Extract the files to a temporary location and transfer all files into the Minecraft.jar folder
Step 3) Start playing and enjoy!