The 9" in aftermarket form is a stout piece, no doubt but you can't use any Ford parts in it or it's just another junker. The reason the pinion is supported on both ends is because the Ford engineers didn't design enough space between the front two pinion bearings. So they inadvertently designed a rear that drag racers would like because of the third bearing. Even a blind squirrel finds a nut once in awhile.

As for the 8.75, I have one in my car with the AL center section but I use only pro gears in it as I've broken a couple street gears and yes I leave on a transbrake. The drawback is the pro gear is only available in one ratio, 4.86:1, so I tend to build my car around that rather than the other way around. I used the 8.75 because that was what I had at the time. If I ever explode it though I'll probably replace it with a Dana, I don't need the 9" or the expense of it.