When did 351w deck heights change?

Short version: When did the deck height of 351w change from 9.48 to 9.503"???

Long version: I finally scraped enough gunk off of the side of the block to see the casting number on my 351w. It reads D2AE-6015-BA13 and 3K26. So if I'm decoding this correctly its a 72 casting produced on Nov 26 1973. So I started searching around to verify when the deck height changed and seem to find three answers:

1) All 69-70 blocks were 9.48, all 71 and later are 9.503
2) Change over in 72, Casting D2AE-B represents the start of 9.503 blocks (from Wikipedia)
3) Change over in 74'

I had always thought it was option 1, all 71' and later blocks were 9.503. The FRPP catalog has engine specs in the back, and backs this up. I tend to believe that Ford would get it right in a technical publication like that.

What say the rest of you?

All the research I've done over the years indicates that the 69-70 blocks were 9.48", and all later blocks were 9.503

I had always thought it was option #1 also. If I thought wrong, it would good to know.

At least the block I have is a D8, so I know it's a 9.5 deck.

in my experience, option #1.

#1 Mine was a 9.5 block and my pistons were for a 9.48. The block was cut to 9.48 to get the compression ratio I wanted. Pistons for a 9.5 block may or may not work in a 9.48 block.

Doesn't really make any difference when the change occured, there's only a .020 difference which is easily removed when milling the decks to true them up anyway.

Thanks everyone. Nice to see a consensus.

I hear ya D. Hearne, just wanted to know what I've got before it goes to the machine shop.

If it's a good shop, they'll mock up the rotating assembly to see if the decks are square and determine the deck clearance, to determine if the decks need to be milled and how much to remove. I have an engine builder/machinst friend that did the work on my 331 and he told me virtually no block that he sees have square decks.

x2 i wacked 2 hundredths off my deck for just that much more hood clearance (every single last thousandths is needed) but mainly because my diamond -32cc pistons were for the 4.8 deck height block. I had to keep my CR below 9:1 for boost.

92 tbird 408w turbo under the stock hood

as stated its not much of a problem at all, i had to get new pushrods with a length of 7.55 with my 351w roller block wacked down to 9.48. I have a ford racing f303 hydraulic roller cam and rhs heads.