Don't mistake "can" for "should."
When someone says "no" that is their opinion that you SHOULD NOT be doing this. There is nothing stopping you from ordering the parts, and installing them on your truck. Many garages will be happy to take your money in exchange for installing these parts, and they will not bat an eyeball.
There are several on here who are overloading Tundra-sized trucks successfully. There are also many others who were happy, but upgraded trucks and were amazed at the difference. There are also some who tried and decided it wasn't for them, and ended up upgrading the truck right off the bat.
Make your own decision.