[clay68c10]

I did ok on the one I got, I'm in it for about $100 and can spend the same or less than what I would have spent on my 12 bolt for it to get posi, c-clip eliminators, and new axles if the bearings go out (which is common).
I don't think the 28 spline count is a huge deal, I'm not making a zillion HP and there were a lot of 28 spline 9" behind factory hi-po motors.
I'm looking at it from the perspective of going thru the stock 12 bolt from top to bottom vs doing the same with the 9". The cost of new 12 bolt axles was my main consideration; any time the outer bearings start to go bad, it kills the axles.
I think if you can get the 9" cheap, it's worth it. Any more than $150 and it starts to go the other way. It also helps if you fall into the right gearset, the 9" I got has 3.00 gears and I'm running 3.07 in the 12 bolt I have now. I'll probably switch to 3.50ish gears after I get a 700R4, but that's down the road a ways.
As far as the discs go, those stock Lincoln discs are close to the same size as my 73+ discs in the front. That should be more than adequate for my uses.