I bought a set of pistons second-hand but they came with no information sheet. I would like to know if they are 2618 or 4032 alloy so I can set the proper piston to wall clearance.

They are +.060" 426 Hemi pistons. Under the dome they are marked with the arias 'A' and the 'Speedmaster' logo. There are no other marks or coatings.

Skirts measured at 4.308"
Compression height measured about 1.765"
Dome Height is about .515"
Total Height from pin centerline to top is 2.28"
Dome volume is about 85cc
Pin diameter is 1.094" retained by spiral locks
Rings are 1/16, 1/16, 3/16

The skirts have a couple oil grooves going around them.
The wrist pin holes have 2 oiling holes per side. (4 per piston)

They may have been sold new to FHO in Canada in the early nineties. Know its a long shot, but any help would be much appreciated. I already E-mailed Arias so far, but haven't tried FHO yet.