1600cc 356 pistons but which ones?

[icemanhd]

Came across these on the shelf at a buddy's shop, 82.5mm bore (stamped 82.45) and they appear to be the long skirted pistons for the non counterweighted crank. I've dug around on the internet but haven't been able to verify which motor they would be for or from. Any help is appreciated. They are all weighed/labeled and oddly one of the pistons is marked/indicated to be heavier than the others...

[Daves911L]

3 are flat top normal pistons, 7.5:1 CR, 60 hp, used '55-'63. But only 3. The heavier one is a C piston, 8.5:1, 75 hp.

[Baz]

I have a matching set of pistons and cylinders - big bore. NOS. Also a set of rings for them...

Not for sale...just bragging.