1/4 mile vs 1/8 mile

You need to choose a rear tyre with the correct roll out to give you the mile an hour you want then cross reference the MPH to ET on any number of online calculators. the Start Line Gear Ratio will be first gear ratio x rear gear ratio. Then you need to look up what you need based on vehicle weight. So you want to run 120 MPH or so on the 1/8 mile you will need say 4.88's with a 31" tyre @6500 rpm. SLR is 2.45 x 4.88 = 11.95 but things like engine stroke and vehicle weight will determine what is optimum for your deal.
So the SLR will get you off the line the tyres will give you the MPH which is directly related to ET. Bit of time with a calculator will save you a heap of money buying parts that may or may not work together.