need to lower my 70 lwb

[70CHEVYBB]

I would like to know how low I can go with my 70 lwb with out doing a c notch and how low with one. Do I need springs and spindle's or just spindle's in the front. Who's kit would be good to use. Right now my truck sits on new stock sb springs in the front and new stock springs in the rear. I want it to be level and at what point do I need to run the exhaust through the frame where the trailing arms attach. Any info would be good and some pics of finished trucks would be even better.

Thanks, Wes