In my opinion the stock manifold even Extrude Honed is never going to pass enough air to let that 347 breath, you need a Holley or TFS intake, or a Edelbrock RPM. If you do not give the motor all the air and fuel it is made to handke then it will never make the power it is capable of.
As for suspension there is no miraclr cure for traction no matter what parts you have. I have full suspension, 70/30, 50/50, Eibach drag launch kit, SSM lowers, boxed uppers, sub frames, no front sway, I ran 26 x 10.5" M&H RACEMASTER DOTS, and yet I still can't hook on my new combo. the best 60ft I have been able to muster out was a 1.98, most are in the 2.4 range and it still goes 12's. On a basic stock motor, stock heads,cam,intake with the same suspension set-up I pulled low 1.6 consistantly. My new motor and cam combo doesn't com on till 3500 so I have to come off the line hard to take full advantage of my power anything over 2500rpms resulted in masive Wheel spin, I even spun them in third gear! (I have never done that on a pair of sticky tires) I have been using these tires for a while so I no how hot to get them on so forth but the motor is a whole new ball game. So as mentioned if you can't get the power to the ground then all the power is a waste. Your car should be 12 second capable but a lot resides in the driver. I have driven my friends car to a 12.89 his best is 13.32, go figure?
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My Ride Check Out My Site 91GT, Holley SysteMAX II Kit-Heads 2.02" x 1.60",Full MAC exhaust 1-5/8" Long tubes, 2-1/2" O.R H-Pipe, 2 1/2" cat back, 12" K&N Filter, RNH PERFORMANCE Ram Air, Ron Davis Radiator, Full Suspension,3:73's, Welds, Best on new motor-12.60 @ 108, no traction 1.98