Well, it was a 318 race block. Bummer. No T/A marking. 🙁
So it was a 340 X block? They said 318 but X Blocks were known as 340 X blocks
You do know they were cast saying 318 and had a small rough bore.
Bore was so small on some thet could have been 273 but could take 60 OVER 340 as well.
High nickel content
They made X Blocks 2 and 4 bolt. added materials where needed.
Stronger than a T/A block and made in quite a few,ways.
X Blocks go for good $ unless toast
They were the "IT" Block before the R Blocks.