No matter what people on here say, there is no way that a slightly modified GT-40 intake is going to supply enough air to an AFR 185 headed 351. I had my old grocery getter running faster then you with probably 100 less RWHP and RWTRQ, and about 10 less MPH. I had an off the shelf Street Heat intake, stock cam retarded 4 degrees, and stock heads, with all the bolt-ons and if I do say so myself, a damned fine tune. I never had it dynoed. But for what I had I was comfortable with mid 13 second runs.
Your combo is not matched correctly. You need to make the call, whats more important, aesthetics or performance? You can always save the GT-40 and swap it on for shows. Keep in mind that the Cobra R wasn't intended to run past 6000 RPMs. In fact, the factory fuel shut off was 6000 RPMs. So perhaps that bit of information helps you out... you're running an intake not intended to make it past 6K.
If you want to make the most of that engine, get an intake on there that will take you out to 6500 rpm shift points, and will have you crossing the line at 67-6800 in 4th gear. The R or the Victor EFI would be a good start... I lean towards the Edelbrock part only because it seems like Edelbrock and AFR produce great results. 4.10 gears are a minimum, I'd look at 4.30's.
This is advice to lower your ET... I personally feel that the dyno is useful for tuning purposes and sanity check purposes. Don't get into the habit of trying to correlate dyno performance to ET.
Adam