Thoughts on swapping a slant 6 with a 383

First off, you need to have a plan for your motor mounts since Schumacher is in limbo. If you're looking for a bolt-in solution with the /6 K frame, your options are going to be severely limited. If you can fab, no problem.
Power steering is doable, but depends on what you decide to use for exhaust: headers, HP manifolds or factory A body B engine manifolds. Each one has their quirks and fitment issues, nothing but the factory A manifolds are a guaranteed "no mods required" fit, and they're pricey (and restrictive).
Clearance with the heater (blower motor) shouldn't be an issue with a B motor, but RBs do.
Whichever engine you choose, you'll need different transmission, radiator, brakes, and probably torsion bars and rear end from the /6 stuff.
Good luck!