Am assuming the OP is now talking about his 'new' 2500HD (fake 3/4 ton,
it's a 1 ton)
This is a higher class truck than your half ton. The 'HD' suffix takes
it into 1 ton territory
The truck is heavier just sitting there with nothing loaded in/on it
Notice where the half way point is...on most TV's it is at the drivers
door's rear edge.
Meaning most of the stuff loaded in/on it will have 'most' of that
weight on the TV's rear axle
Then that this is several thousand pounds more in initial weight
and capacity...it will need higher class tires than your half ton
and need more PSI
You need to change your half ton metrics (+6K-7K GVWR) to your new
+9K GVWR truck's metrics
On the spare...do you know which tire position will need it? No one
does, so air it up to the max any one of the four on the ground would
ever have...if it goes to one where it has less PSI...just let out
PSI...much tougher to air them up out there in the boonies...