As said before, go thru the front suspension and make sure it works correctly and has at least 4-5" of travel. Make sure it is LOOSE!
If your rear shocks currently are not long enough, that may be part of your problem as well. When I was using SS springs I had the longest CE adjustable drag shock I could get. My best 60 with ss springs was a 1.412 running 10.60's.

Now for caltracs, I had all kinds of troubles when I switched to them with the monoleaf springs. I was running strange double adjustable rear shocks without the coil over springs. When I called calvert for help, they told me those shocks were too short. I ordered their shocks to finish off a complete calvert recommended parts list and their shocks were only a 1/4" longer. Still had the same problem unloading the tires. Called John Calvert himself and once I told him what it was doing (I had told his tech assist guys the same thing 2 times prior) he immediately asked how much front end travel I had. That was the problem the whole time. I had about 3 3/8" travel. Once I corrected the front end travel and now have a shade over 5" it has been fine. Still a little finicky on greasy tracks, but what isn't. Current best 60 is 1.349 running 9.899. They all have inherent problems and advantages. It is up to you to figure out what you can live with. HTH Beep