If you're that concerned about losing 2 days and consider this critical path, then use something other than Grade 8 for the purposes of marrying everything else. You can swap in the Grade 8 stuff when McMaster opens up on Monday.
That way, you can mock everything up, marry the trans and motor, torque it all down except the motor mount thru bolts and just replace those before putting the powertrain back in the car...
...or just wait 2 days and enjoy the weekend
