Is the deck completely round or is the right side squared off? 33" decks were snapper HiVac decks and were completely round while the 30" decks were a standard deck and had a squared side. Also, the proper way to measure a lawnmowers bade is diagonally (blade tip to blade tip). The measurement will be slightly less than 33" (I can't remember the exact measurement for 33"). This could be why your blade measures so much smaller. Lastly, next to your model number is the serial number. The first number of the serial is the year the mower was made. All you need to know is the decade. For instance, if you know the mower was built in the 80's and the first number is a 5 it was built in 1985. Hope this helps.
