Help identify a tri power manifold

[tx_stratdad]

Can anyone tell me anything about the two large X's, cant seem to find anything about it?

 

[oldskydog]

Can anyone tell me anything about the two large X's, cant seem to find anything about it?

There is no specific written documentation on the use of the X that I am aware of. It appears to be a symbol used at the casting foundry to indicate a change to the mould/pattern or its metallurgy.There are many examples through the years including 58 283 engine components, 62-63 461X 327 heads, and the late 62 up W blocks.
I have a 58 intake with one x probably indicating the first change to the original casting and yours is probably the second version.JMHO
:

 

[Buzzard II]

I also have an early built 58- 348 engine. Mine, like yours was built in 57. I have the original water pump with mine and it also has the two xx's. I haven,t seen the 2 xx's on any other year 348 intakes, but.....
Bob