1/ Search TC forum for "weight police". Read through some of the discussions and make up your own opinion which side of the discussions you favor.
2/ Weigh your truck, get both axle weights.
3/ Compare actual axle weights with axle ratings on your door sticker.
4/ The difference between axle weights and ratings should give you a good idea of what the truck can safely do, even without modifications.
5/ bonus: try to understand the relationship of the position of camper COG and the resulting weight distribution of the payload between both axles.
In my opinion, it will handle a 650 just fine, but you will be over posted GVWR.
Chances are it drives OK without modifications.I would not modify before I have tested how it handles first, then address specific issues.
Just try not to exceed the rear tire weight ratings.