Ever see those NHRA stock eliminator 440's ripping off 10's??

Pistons have to be NHRA approved replacements..... Stock weight.
My car went 10's for years with heavy trw's...... And that was 20+ years ago.

New lightweight pistons are great, and if I were building a new motor for a 550hp+ type application that's what I'd use for sure....... But if I were looking to make the best use of my money in terms of improving my ET........ They would be very far down on the list(unless they came along with a stroker crank).

A good converter will be the biggest instant improvement to the ET.

At 3670lbs, with a 383 that also has heavy trw's in it, at that same track you were at, my car would 60' in the mid-1.50's.
Good converter.