Craftsman YT3000 deck too low, at highest setting

I purchased a used Craftsman YT3000, this specific item is:  917-288516 .  Its about 8 yrs old or so.  At the highest setting, the mower mows about 3.5", but I want to shoot for 4".   Reading online, others have this problem. Tires say 15" front, 20" back, but measured diameters are closer to 13.5" and 19". 
 
Question: How can I put larger tires on (would require likely wider diameter hole wheels) to boost the height?