Sounds like your on the right track, you can use the stock line. Ideally you want the pump lower than the tank so its gravity fed. It doesn't have to work so hard that way. The rear frame rail is a good spot. You didn't say where your mounting the regulator, if your not mounting it under the hood keep it as close to the engine as you can. Run a #6 line to the carb. If your running a holley set your pressure at 6. Edelbrock/Carter set at 5 psi.