If you look in the timeslip forums (click on Quick Links) and look for 14 sec 3.5's, you will find some, even 13 sec cars with 3.5's. You could PM some of those guys, ask what they did. One fairly cheap mod would be nitrous. 100 shot could net you 1 sec off your quarter mile time. There are many mods available for the 3.5, depending on how deep your pockets are. It's certainly a stout motor. Check out E55, he's running 12.58/112 mph with a 3.5 powered Chrysler 300. Of course, the faster your car gets, the faster you will want to go.