Heater box installation question M35A2

I know this must be somewhere here already, but I cannot find it.

I am installing a cab heater box in an M35A2.

I have the installation kit, the two steel pieces. I bolted them together (they only go one way.) and fit them into the engine compartment.

For the vertical piece, do I drill the holes on the fender. or through the frame rail.
The way it fits it appears to be through the frame rail. I do not want to do that without confirmation.

Thank you in advance.
Rodger

I found an answer. Holes need to be in the frame. I can not figure out how to delete the post.

Rodger

The vertical piece bolts to the top of the frame rail- the horizontal platform through the sheet metal.
Hope these pics help.

Thank you, Woodsplinter.
And excellent photographs.

Rodger

Unless you are restoring, mount it in the cab below the glovebox, route the water instead of the air through the firewall. You will lose much less heat and make a much smaller hole for cold air to enter the cab through. You might even look at a M923, the heater box mounts to the engine side of the fire wall and on the inside of the cab the air box is mounted. No more three or four feet of air ducting.