Lane from the Pirates is running a d44 and a d60 and 38.5 swamps with a mostly stock 22re.  He has broken a lot of 21 spline output shafts and is not too hard on the throttle.  Im not sure how much stronger the 23 spline output is and I know of a few chevys running marlin 23 spline cases. Dont get me wrong, I love my marlin t case and probably wont break my output, but I would rather run something bigger like an NP205 or an Atlas when running a V8.