Camaro clip is the easiest route.
'70s Camaro clip is common and cheap to buy. It is also strong enough, gives you power disc steering/power brakes. You also get a standard Chevy bolt pattern, and engine mounts for Chevy engines. You also get a lot of aftermarket choices for the Camaro clip (anti-sway bars, shocks, ...).
Sure, you have to weld it in...
I have often read that Mustanfg II is too lightweight for the job.
Stock axle looks "old school", but will never be an independant suspension...

'57 Chevy Suburban; '70 Chevy Impala.