placement of multiple air filtration units AND modine heater

Background: I'm in the process of turning my 3 car garage into a part-time woodshop. I picked up two air filtration units, JET AFS100Bs to be specific. I understand that I want to hang the the air filters from the ceiling at about 8' on opposite walls so as to create a circular air current around the room. I've also put in a gas line for an eventual heater for the garage, probably a Modine Hot Dawg or something similar.
Question: Given that the gas line runs up the south wall, and the east wall/ceiling is out of the question because of the garage doors, what would be the optimal placement and orientation of the three units?
1) Should the heater and one of the air filtration units occupy the same wall or would it be better for them to all occupy different walls? 2) If they do share a wall, should the air filter be upstream or downstream of the heater? 3) Should the heater point out into the middle of the garage or downstream? 4) Am I crazy for even thinking of installing a heater like this in my garage because of danger of explosion or fire?
Thanks in advance for any direction you can provide.

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