it is an autometer sport-comp. the trans is a 350 and 4.11 gear the the speedo reads like i am going 20 mi. faster. is there an adj. on the speedo or trans? what can i do to correct this?

There's a little plastic gear in the tranny where your speedo goes in that needs to be changed. They have different colors for the different # of teeth. Due to tire/rear axle changes, your existing gear has the wrong # of teeth now. I don't remember how to calculate the correct #.

thanks, any one know the formula to calculate the proper gear.

Check out Fred Aldrich's website:
http://members.core.com/~faldrich/speedo.htm

He's got a bunch of interesting stuff there including the speedo gear stuff.