I have a PO Safari where the dealer (believe it or not) replaced the original heater with a newer and smaller model. He elected to use the existing exhaust ports, so the heater was placed on a box to give it the right height. Ugh. Wasted space. So while remodeling the whole cabinet, I moved it. Much happier now.
The old cabinet (with the awful tambors) with the heater sitting up on its box.
The new location, with a new plywood duct for the hot air, and a printed grill (you can't buy a 4x6 grill, as far as I can tell).
I had to patch the outside when I moved the vent. One issue I didn't account for was the increased curve of the shell down closer to the C channel. I couldn't get the vent to lie flat, so I printed a 3/8" wedge to go under the bottom half of the vent plate.