I was in a similar boat, I needed to replace a miled out 2003 2500HD with a 6.0, but I just wasn't going to pay covid prices and luckily stumbled into an identical low mile 2004 with the LLY duramax for a couple $k more than I got for the old truck.
There is something about the GMT800 platform.
Yes it has a few issues that are well known but overall, there is a lot to like.
I've had my truck for 20 years, 150k miles and it still brings a smile to my face.
I know on my 04, the 33 fits in the under bed OE location, with the 17inch H2 rims. Maybe worth double checking? I may have pulled a heat shield, I dont actually remember at this point.
L
ong winded story
OK, your making me do my homework now.
I'm old school and plan to carry 2 spare tires.
I know 2 spares are going out of fashion now, Andrew SPW (4XOverland) and Ronny Dahl both are switching to a single spare.
(I prefer YouTube over TV - I'll watch what I want to watch but it's way out on the fringe apparently)
I've been in 3 situations where more than one spare was required, twice as a kid traveling with my parents and once as the responsible adult.
In the early 70's my Dad made a tent trailer from a teardrop donor trailer.
He set up the trailer to have the same bolt pattern as his Jeep Wagoneer.
I was a kid so I don't remember where we were but we ended up taking a tire off the trailer and going in to Barstow or Mojave to get 2 tires fixed, then back out to recover the trailer.
In the late 70's we lived in Australia for 5 years.
When we left Dad and I made a tour from Alice Springs (where we lived) to Queensland and back to the NT in Moms' Holden Sedan.
Dad had arranged to sell the car in Darwin and we would board a plane back to the US.
We planned to take the Barkly Highway from Tennant Creek to Mt Isa.
But 50 miles from Tennant Creek we shredded a tyre.
Dad suggested we mount the spare then make lunch and plan what to do.
The fly's where so bad we threw the tools in the boot, hooked a U-turn and retreated to Tennant Creek to replace the tyre.
I still haven't been to Mt Isa.
20 years ago my wife, kids and I lived in Japan.
I stored my toy hauler at my brothers place in Lancaster California.
After moving back to Ohio we went out to pick up the trailer.
On the way home we had 2 flats within an hour of each other.
I ended up dropping the trailer on the side of the interstate, driving in to Deming New Mexico to buy 2 tires.
Back to the trailer and back to the tire store for 2 more tires.
Note - the shelf life of tires is different between Ohio and Lancaster out in the desert.
Can a 33 fit under the bed?
Yes - but.
I spent some time switching out a spare with one of the front tires and took some pictures.
This is my current spare, it's a Cooper Discoverer in the stock size.
The tire hangs down to the same level as the OEM trailer hitch receiver, I measured 15" clearance.
And this is a picture of one of the 33s in that space, I set up a jack stand to get the phone the same height off the floor.
This is 12.5" to the floor.
So, my preference will be to carry 2 spares on the back.
Will I ever need the 2nd spare?
Will I ever need the 2.5" of extra ground clearance?
Probably not on both accounts but it will be there.