Ideal "in cage"/"walk around" weight formula - (((Height in cm + Reach in cm)/2)-100) = Ideal weight in kg; then, (Ideal weight class in kg x 2.20462) = Ideal weight in pounds.
Ideal "cutting" weight formula - (((Height in cm + Reach in cm)/2)-110) = Ideal weight class in kg; then, (Ideal weight class in kg x 2.20462) = Ideal weight class in pounds.
Therefore, at 6'3" with a 76-inch reach, Pena should be walking around at 202.32lbs, and fighting at a minimum of 180.27lbs, or in the 185lb weight class.
Eat like an adult, train like a professional athlete, and you'll add the requisite size to match your height. Then nut up, and fight in a division suitable to your frame.