Which heater and where?

[stinkity stoink]

Question for the heat guys. I have a 24x26 garage with 16' ceilings in Nj. Pretty well insulated 2x4 wall with r19 and roof has r30. One side of the garage has a loft which makes the ceiling in that bay 89-1/2" tall. I would like to hang the heater on that side in a corner and direct vent. I see height charts that say don't hang it above about 10' ,but don't really see a minimum height. A quick calculation out there would put me about 73" to the bottom of the heater. Is that o.k?
I am also trying to figure out which heater I should get. Sterling, hot dawg , big maxx. Looking around 45k btu.
Thanks