Windsor block question

[91Notch]

I have a 351W block I pulled from a 1970 Ford
I pulled the motor and the block and heads both have F1 part numbers instead of the F0's :dontknow:
The car belonged to my grandma, she was the orig owner. The motor always ran great and was never removed/replaced so what gives? :dontknow:

 

[orangejuiced86]

MIght have been a late year build?

 

[82hatch]

MIght have been a late year build?

What he said. They did some strange shit in the 60's early 70's.

 

[91Notch]

MIght have been a late year build?

That's what I was thinking too