Well, finally got my s*** together and installed the Webasto. Waited until AFTER our -40 cold snap naturally, but whatever.
Took out my relay box holder thing.
Cut up the relay plate and made new mounts for it where the old 24v switchover relay was living.
Built a plate with mounting brackets for the heater.
All mounting plates this far (including the battery boxes) have been using factory threaded holes, by the way.
Picked up some 3/4" and 5/8" silicone heater hose, with 2x reducer fittings and one 3/4" 90 elbow.
Used a brass T fitting with 1/2" barbed ends and a 3/16" reducer for the heater fuel tap off.
Built a little standoff to mount the fuel pump right to the heater bracket.
Ran the exhaust down the shock tower to the frame, again unused factory threaded holes.
Ran controller wires into the cab, cut and soldered them shorter since Webasto gives you 9 miles of the s*** (will say that I'll just get new crimp pins and wire the connectors properly without a soldered splice, but who knows when I'll get around to actually looking up which parts I need)
Mounted the controller behind the shifter with some 3m tape for now. I didn't want to commit to screws, this might just stay like this.
Ran the main power for the heater to my auxiliary fuse/relay panel and used a 20a fuse there instead of the inline one they provide.
Truck started up instantly. No leaks whatsoever. Tried the Webasto, started immediately. Then shut off after a minute, gave F01 fuel error. Looked at everything, checked it all out, tried it again. Started up, sputtered a bunch of white smoke and chugged to life like a tiny little old diesel engine. Smoke cleared after it got going, let it run for 15 minutes, seems to be fine now. Tried it again a couple hours later, fired up good, had warmed up the lines in about 5 minutes. Still no leaks, all looks good.
Will actually test outdoors tonight.
I did not look at my wireless system yet about connecting my trunk button to it, but gonna do that.
I did not connect the relay output from the Webasto to the heater blower circuit yet. Gotta look into that one too.