89 GT. X-303 cam

[420nitro]

Need alot more info.

The cam has 4 degrees of advance built in. When you retard 6 degrees on a multi-index cam gear it is actually 2 degrees retarded from straight-up. But any ways when you retard a cam....it brings the power in later. Basically the power band has been raise about 1,200 rpms in a typical 302-306. Your 331 makes the cam seem smaller because of the cubic inches. So actually it has a power band to close of what it would be in a regular 302-306 cubic inch motor now.
I never liked that cam plus it's really out-dated by todays standards. I would look into some other proven camshafts like the comp-cams extreme energy if not the TFS grinds. It all depends on WAY TO MANY variables. We need alot more info of the entire package of your combo.

But for a 331 to run high 12's at that mph is off unless you are in REAL HIGH elevation. ( for a motor built for racing in N/A trim.)