Fourgear, that's exactly what I did when I built my 9". I used an aluminum Winters housing center and had Dr Diff build me a set of tubes the size I wanted and put mopar ends on the tubes. I was able to reuse both my 35 spline axles and my Wilwood brakes. Saved a few bills for sure. If your spool is splined all the way through you will probably be able to use your axles, mine was and it all fit together. The unknown in my case is the Winters center housing however I did add some additional bracing to help. I'm using a Moser thru bolt center, pro gears and a monster 10 bolt pinion support I found years ago. I haven't run it yet so this next year will be the test with my new blower engine.

BTW over the years I have had excellent results from the 8 3/4 unit I have used. I've only broken 2 R&P in over 20 yrs use and that's behind 550 to 650 hp smallblocks with transbrakes, big slicks and street gears, no wait, one set was a 4.88 progear.