Old Arias Forged Piston-to-bore Clearances?

Hey all,

I am taking a long shot that someone in this knowledgeable crowd might have some old Arias piston experience. I have a set of old Arias forged pistons that are probably 15-20 years old, that I am planning on putting in a block for street use (not a Mopar, but Opel 1.9L). I have had them over a dozen years. I'll take a wild stab that these were custom machined off of castings for Chevy 305 pistons... the piston diameter is 3.680".

My machinist and I are debating the clearance to run... my only experience in using forged pistons in this particular engine was with the old TRW and Hepolite's and I would run them at .0035 to .004" with no issues rallying. He is thinking more like .006", which I don't like for just running around on the street.

Under the crown they say 'Arias' and 'Alcoa' and '40' in cast letters. The material coloration is bright aluminum, rather than any sort of light grey like the old TRW's were, so IDK on the actual material. And, there are no steel strips in the skirts to manage expansion like in the old TRW's. So any ideas on the piston-to-bore clearance would be appreciated.

Thanks!