Short answer. Yes, you’re crazy to do that.
Back to basics:
Tow ratings are GCWR minus truck curb weight, full tank & 150# driver. IOW, your truck Load Capacity is part of the towing capacity.
So if you buy a TT at/near your factory tow rating, you have no payload left.
I recommend looking at the TT GVWR (figuring it’s too easy to fill it up, unless it’s a toy less toy hauler) and using that to help determine your choice TT.
Best method to determine available tongue weight on your truck is to load it up like for camping, people and all, throw in the WDH, and weigh it on a CAT Scale. Subtract that from your GVWR and that’s your remaining load capacity. Then on the choice TTs in the ranges you are looking, add 2-300# to the empty tongue weight for a closer to ready to camp value.
A non weighing option is to look at GVWR of TTs nearer 75-80% of your tow rating. Then crunch the numbers.