I'm curious before I overclock this i5-760 from 2.88 GHz to 3.45 GHz if I should have more than 4 GB 1333 MHz of RAM? Will overclocking this about 20% require additional RAM to run well afterwords? Currently I am not exceeding my RAM usage but I am worried that I will be after the overclock.
When people talk about overclocking affecting memory, they are refering to the speed of the memory, since the speeds memory and CPU are generally linked.
If your CPU can clock faster than your ram, than you might be "ram limited", this doesn't mean you need more capacity, it just means that you have to change the multiplier on the RAM to the next lower setting (like 1333 to 1066) so that the ram doesn't overclock outside of it's tolerances.
First off, I'm curious where this "3.45ghz" comes from? Have you already planned what base clock and multiplier you want to use? If yes, then you can already know what RAM speeds you'll have... it's either 6x, 8x, or 10x multiplier (10x base clock). If your RAM is rated for 1333mhz, it'll probably run fine at the same timings and 1400mhz, then you'd want to aim for 1600mhz and increase the timings by 1 (8-8-8-24 becomes 9-9-9-27). Or you can go the other way, like 1200mhz and decrease the timings by one (7-7-7-21). This is assuming 1333mhz CL8 RAM.
However, if "3.45ghz" is just pulled out of thin air as a target, then I suggest not worrying about that. Think about what base clocks you can use to achieve a stable RAM speed. Example: 160x10=1600mhz RAM, 2.860ghz CPU. 175x8=1400mhz RAM, 3.85ghz CPU. This is assuming you're using the highest multiplier, which allows turbo boost (on my i5 750, I found 180 base clock to be the highest which will allow turbo, without needing to exceed Intel voltage and heat specs).
Alternatively you can use 200 base clock, with lower multipliers. Say, 200x6=1200mhz RAM, or 200x8=1600mhz RAM and then you could try 200x20=4ghz CPU, 200x18=3.6ghz CPU etc. This is the "fun" of overclocking... you have to try different things to see what'll give the best results - speed, low temps, low voltage, stability etc.