I didn't asign a value difference in dollars because it's impossible to do, what i'm saying is that there WILL be a value difference and it will be substantial, and there will be an even bigger demand difference because there are many people looking for a numbers matching car that will not compromise and will pass entirely if one number doesn't match. The cost of a 340/360 shortbock assembly can vary between practically free and a few grand, a small price to pay to ensure and preserve a cars #'s status and pass on the gamble of running the original block. Yes, it's rare to break a stock block in a street application but it does happen, 340's are thin wall blocks and I've seen many of them crack just from hot or cold weather. IMO it's a no brainer decision, but to each his own.