depends a lot on the state of tune of the car, grade of fuel being run ,track conditions , and the weather/density altitude where its racing , my wifes regal gs went 14.4 @96 with only a K&N filter.
this was a week after I watched an identical car run 14.5 no mods
other car was also a local forum member who like me had run several w bodies at the track before and we get good weather/altitude for racing
take those same cars to denver or florida in the summer to race them and they would probably run 15.5
best thing to do is take it to the track and race it- once you get some passes it will only get quicker
stock trap speeds should be in the low to mid 90's