Tires have many other responsibilities other than just weight carry...and the PSI is also NOT just for weight carry...it more to hold the tire's shape during its duties
The vehicle door label tire listing is the MINIMUM tire specification to meet that vehicle specifications
Also, the letter designation is only for its "ply rating" and not even how many actual plys it has
When re-engineering the OEM tire with different size/rating, more than just its weight carry rating must be taken into consideration. Of course within the same class tire. Going to the next higher, say commercial, will have an 'E' with way higher ratings
At least the OP is staying in the same class tire (LT) and not dropping down in class (P) rated.
Suggest reading up on how tires are rated and what those ratings mean.
It would be illegal in other countries who enforce ratings of vehicles & their components...to go lower in rating
Ditto wheels...the new re-engineered wheel must have equal to or more spec vs OEM