18 spline abody box?

I thought you could buy an A body 18 spline box over the counter from direct connection.

Did the put them in "normal" A body, non SS/AA cars, from the factory. Nope.

23 spline transmissions are pretty tough.

I agree with Crackedback the 23 spline will be more than tough enough for you. If you have any questions just call Brewers or Passon Performance. They will be able to answer all your questions.