for what it's worth, when I put an A500 in my M body, I think I was able to reuse the slip yoke from the original 998 tranny..IIRC I just had the stock driveshaft shortened...or did I pick up a 7290 ujoint 727 driveshaft to have shortened?...that was 18 years ago and I'm getting old and forgetful
you had to have also swapped rear ends....most M bodies Ive come across had 2.2 or 2.45 rear ends stock..... I had one with a 2.9, still too low for an OD to work