Stretching and Lowering?

I am new to the bike world so, I am just asking quesions. If I was to stretch and lower a new street bike say a Suzuki GSX-R600. I heard that I would need to make some engine modifications to make up for the stretching and lowering. What type of engine modifications would you guys recommend for me? Also, what type of brands would guys think are good and reliable brands to use for stretching and lowering? Also, what would be another good and reliable brand to buy the engine parts from? Thanx guyz and have a nice day. Later!!!