For front coil overs use 275-350# rate. You could start with 275# and test it. If you feel more spring is needed, up the rate in 25# increments. Different chassis combos will work better with the different rates.
Since the coil over is twice the distance out on the control arm as the stock coil location use the following rule of thumb. To get the coil over rate take the stock location rate (or performance coil) and divide by 2. This is the approximate coil over rating to match. Note the coil overs respond alot differently than the heavier stock location due to lower unsprung weight ( in your case lighter A-arm). Conversely doubling the coil over rate gives an approximate stock location spring rate. This is helpful because everyone advertises rates for the stock location. Stock location rates above 700# are considered race rates. Spring rates above 800# are all out race. Therefore a coil over rate greater than 350# for the front would be considered a race rate that would be rough on the street.
For the best tuning install rear coil overs also. This allows you to set corner weights to compensate for understeer/push or oversteer/loose conditions. Setting up the car correctly can make for really fun on-street and highway performance.
As a side note ensure to get ajustable camber/caster plates and a strong strut tower brace. I recommend Maximum motorsport for both of these items.
Have fun!
Mike
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