Identifying features of a mountain bike specific to a tall and heavy rider?
I would be looking at bikes with frames made of steel. A cro-moly frame will be most likely to meet the requirements you are looking for on your budget, and there are a lot of bikes with cro-moly frames available in different price ranges. Companies like Trek and Diamond Back make high quality bikes in every price range, you would just have to look at how each bike specs out for weight limits. Dont rule out alloy bikes, I just think they tend to fatigue faster under rigorous use. There is a company called Zize Bikes that might interest you, although they look pricey.