18 spline gear box in a early A body

so let me start here. i am a complete novice when it comes to this trans. i am building a turbo 5.7 hemi. i refuse to put a auto behind it. i have been looking into using a A833 trans. my question is this. looking at brewers.com i noticed that they offer a 18 spline gear box for the a body. what is the difference between a A body and say a B body gear box? now my second question is this. i have been doing some research but have not found really any answers. if i go this route i am going to try and send my gear set to liberty and have them faceplated. i am also really loving the idea of possible using a v-gate shifter. has anyone done this? maybe you have some info and tips for me? what might be the weak points after this? thanks john