I need the height difference between a small block and big block Frame mount for the motor for a 66 chevelle?

I don't think there is any height difference just shape. I've seen both but never measured them.

Pat is correct, there is no height difference. Take a look at this post (http://www.chevelles.com/forums/showthread.php?t=35977) , it has a picture that may help.

Ken,

Excellent, an old post with pictures is worth a thousand words.