AC to Non AC heater
That's alot of work! This is how I solved my A/C to non-A/C set-up:
First I mounted my non-A/C heater box to see where I needed to cover up the huge opening....
Then I whipped up a new blower motor surround trim.
Here it looks OK without the engine in there.
With the engine in you hardly notice the bigger surround on the blower motor.