I have been lookign around at used heat/air conditioners for my garage/
shop. It is not used all the time, mainly on weekends currently. It is
a 30x30x10 metal building with 2x4 walls in the inside and 2x4 trusses
on the ceiling.

I found a local heating air guy that has an 80's 3 ton unit that he
says was workign when pulled out of the house. The owner wanted to
upgrade. But, it is not a split system like I have in my house.

Is there a way to use this and it not look bad ? I mean, how would you
do the duct from the outside to the inside with a 2x4 wall?

Would this be too inefficent since it is old even though I am not in
there all the time. It does get terribly hot in there in the summer, I
am not as concerned about heat in the winter. I am in the process of
insulating currently and have no inside wall material as of yet other
than studs.

I have a 100 amp panel in my garage.

This unit is 300 bucks.