Based on first hand experience here is my
You will be okay with what you have, however, Get rid of the aluminum belhousing as soon as you can and get either a scattershield or an oe steel unit. You will break the 8 3/4 before you break the transmission. A 23 spline has been in my car since I bought it new in '68. Never have I broken a transmission. I run slicks when I race and actually pull the wheels every once and a while. The 23 spline is a stout piece. Do what you want, these are just my suggestions based on personal experiences.