Proper Riding Horse?

Hey all, I'm a pretty overweight person at about 330lbs, I have never been this heavy in my life until recently and I miss riding the way that I used to. I might be moving up to a ranch in the mountains, and you're allowed to have one horse to board for free. I was thinking of getting a horse, but I am afraid I'm to fat. I talked to a woman today who works horses all the time and she said a Morgan can carry 350lbs easily. But, I am curious as to what type of horse would be best to purchase if any. I'm working on losing weight, but until then my heart is sad that I am to heavy to partake in one of my deepest pions.