Originally Posted by
Beanscoot
The change over date is the date at which Ford switched from producing 351W blocks with 9.480" deck height, to 9.503" deck height.
Ford publications say that 1969-70 engines were machined to the shorter deck height, while 1971-on blocks had the taller height. Both received the same length rods and same (compression) height pistons.
What is the casting number of your cylinder block?
I'll have to get that within the next few days. As of right now, I'm SUPER busy after work and don't have a chance to take a look. I'll definitely get back to you though.