J or U heads ?

[Mike Cooper]

Can anyone tell me if these are J or U heads by this stamp?

 

[318willrun]

J
.............and welcome

 

[Alaskan_TA]

J, but the U heads are also 915 castings, so it would not matter.

(same with O & Z)

Edit;

There is also a newer J head, but that casting ends in 974.

 

[Mike Cooper]

Thanks guys.