Honest 550hp drag radials and a stick in a heavy car....?
I like 8 3.4 rears for street cars. Not that combo though!!! Dana for sure IMO

way long ago in a land before time---SAE engineers rated the 8.75 good at 500 hp and the 9 inch at 450 hp----9 inch flaw-----the pinion is located at the bottom of the ring gear---that is the weakest position----it is strongest at the middle of the ring gear-------yes you can buy alot of stuff for a 9 inch because the aftermarket chased it-----like they chased the sbc....

It should be around there, you can see my other engine threads to get an idea of where it'll be (although certain things, especially the cams I wanted, have been changed to bigger things, ~240@.050, trick flow 240>eddy rpm heads, etc.). I'm just wondering if the Moser 60 as is (or with MW billet caps) would be strong enough, or if there is anything else to strengthen it.

Since the Moser 60 was a redesigned Dana 60, they may know how much stronger the housing is than a OEM Dana 60. As for reinforcing it, you can add Pro Gears, a housing cover "girdle", or whatever it's called, cryo and REM the ring & pinion using a steel billet yoke. I've also seen adjustable bars on a Dana 60 to minimize and flex. All of this would be helpful regardless of what rear end you use. You also have the 40 spline option & 5/8" studs..

The girdle is to help support the caps with preload from the integral bolts. Those covers are about 1/2" thick. I got a Moser 60 with a billet 1350 yoke utilizing u-bolts. Ask 'em. I had an OEM yoke spread a bit over the years on my Dart. It eventually pounded a cap out and I lost a driveshaft.

A Dana 60 will take a lot of abuse without getting too fancy. With the weight of a B-body and a stick, the extra options can offer some insurance, especially if it hooks. But I just like to be extra cautious.

Anything will break eventually, even with a milder combo. I had a W-2 360 auto Challenger footbraking as fast as 10.22 and 1.37 60' times in the '80's & '90's. Not a really big deal, but I literally put thousands of runs on an OEM Dana 60. This was almost all year, twice per week and sometimes 3 times here in Florida. Many track championships to show for it. I believe I broke at least one gear and one axle, but not more than two. The original gear was behind a 440/4-speed that the previous owner had.

I have to back up a bit.....The Moser part PY500 is forged steel and what I got with my Moser 60. Better than cast and OEM styles. I got it confused with the the billet 7260 yoke I have on my Dart 8 3/4. (Haven't put the Dana in yet.) 7290 billet yoke

Aluminum does amaze me with the high stress applications: i.e.: driveshafts, yokes, trailer hitches, etc. But I feel better with steel.

Almost forgot.....I don't know what you have for a driveshaft, but you don't want that to be your weakest link. An aftermarket unit would be much better than an OEM unit and I've had excellent results from Spicer solid u-joints in race applications. I don't know how well or long they will last with a lot of street driving & no way to add grease without disassembly. Otherwise, grease fittings in the cap may be preferable to ones with a fitting in the body between the caps. If using the fitting in the body, orient the u-joints so the torque will be applied towards the fitting as opposed to away from it - if that makes sense.