Whats up with the borg warner transmissions will they fit a 66 chevelle? What about the number of splines how do you know what will work a borg warner i see on ebay says 26 out and 32 in not sure what that means?

Yes ,it'll fit.
You will need the appropriate shifter install kit for the BG
Here's trans. info:
http://www.chevelles.com/forums/showthread.php?t=250379