Anybody ever seen these pistons in what I’m assuming is a stock 350 TBI engine?

i am installing 906 vortec heads on this engine in my chevelle

it is a very fresh rebuild that sat for 20 years...
it is a 14093683 casting block (also says 5.7 LG) It is machined and tapped for roller lifters and mechanical fuel pump, it has 1987 TBI 350 heads on it.

just curious because all 350 TBI engines I have torn down before had the 4 half moon valve reliefs, not the solid groove

 

I'd say aftermarket, measure the bore, probably .030 over.