If you already committed to buy it, then why bother finding out? If I was buying and had a choice between two trucks of the exact same condition and price, one with a 53 block and one that wasn't, then yeah, it would make me go with the non 53... But if it meant paying significantly more for it, or getting a beat up truck because it wasnt a 53 I wouldnt. If I already owned the truck, i wouldnt worry about it either. If it cracks, it cracks. If it doesn't, it doesnt. But if you now find you have a 53 theres not much you can do about it other than get nervous and worry.