Totally Dissapointed!!!!!
They probably have an engine dyno and not a floor dyno. In which case strapping it down doesn't describe it. It has to have the crank hub adapter, bell housing adapter, mount brackets and water fittings. They probably aren't set up for that.
Why on earth would you take your Mopar engine and entrust it to a bunch of chevy and ford geeks? That's the first mistake. Secondly 20W-50 oil is stupid. They obviously have no idea what they are doing. 10W-30 would be the heaviest weight oil I'd ever recommend in a small block.
Now, does it use oil? I still haven't seen what color smoke is being produced. I'll have to wait for your answer to that before I'd hazard any more diagnosis of your problem. Also I'd want to know when does it smoke? All the time, on acceleration, at idle, on deceleration, at cruise, low speed, high speed, cold start, hot soak restart? Many variables here and each one could point to a different cause.