First, decide if you believe in the OEM's ratings or not
If not, then discussions of changes academic...but note that any changes
to the OEM specifications will most likely take the OEM off the liability
hook...
If yes, then understand how their ratings 'system' works
All documentation for any given vehicle is a contract between the OEM
and buyer. Baked into that is the warranty and liability
In that 'baked in' warranty and liability is the COMPONENTRY the OEM
provided from the factory.
By changing a class and/or size of any component, the owner is RE-ENGINEERING
that component and sub-system to whole system
Mainly going lesser, but also going higher in spec. The warranty and
liability coverage is for the OEM spec components and does NOT
include the re-engineered componentry
Yes, when you go larger or higher spec, 'that' component is rated
higher and 'can' do more...but, bottom line is that the OEM docs
(that includes the door label) is still or only for the OEM equipment...
I knew that all of my modifications to my 1973 K5 Blazer (1 ton
suspension...Dana 60 front end & positive arched leaf springs, 14 bolt
rear & higher rate leaf pack and commercial class tires, 14 ply) would still
have GM warrantee it as a 'half ton'...
So if one does NOT like what the door label says...then buy one with
the door label that you do like...and if you don't care for any warranty
coverage and/or willing to take the liability, have at it...just know
what that re-engineering begets you...