At your weight and height from in my opinion, you should shoot for something around a 160-162 and get a STIFF board which most rentals are. If you are considering buying a board, my M3 Discord 161.5 would be a perfect board for you. Every time I ride it I wish I weighed a bit more. The board as far as length fits your heigh/weight as far as Im concerned. People say height has nothing to do with board size BUT I disagree. At your weight I'd say a lot of people would reccomend you go with a 164 or bigger but I personally believe that a shorter person has a harder time throwing a long board around versus a tall person (especially with longer legs). If you are COMPLETELY new it probably wouldn't hurt to go 158-160. I don't work at a shop and am not an expert, but I do believe a board that is told to be too short for you because of weight, can be easier to ride than a board made for your weight if you are a shorter person compared to most people in your weight range.