If those new springs are too low, they should be replaced. Some Mustangs rode low, but only because they had sagged already. Six cylinder cars were the worst, they tended to sag within three years of being new.

This has new GT springs from Glazier Nolan:

 

Thanks all, I could not decide which springs to buy and no one could tell me exactly what the springs would do as far as ride height when I asked the vendors. I belive mine came from Laurel Mountain (its been about 9 months). I didnt want to go five leaf or mid-eye since this is not a high performance car and I'm running stock wheels I didnt want it to sit too high.
I'm not buying another set of springs again, I remember the old shackles (had a set on a 72 Nova back around 1980) but I was hoping I can find some that wont hang out the bottom, and the rear shackles are pretty tucked on the 68. I agree with the air shock negatives also, been there done that on previous cars....

Thanks all,