Help with piston id

[aeroglen]

I bought engine out of car, seller told me it 500 cid. It have Indy 440-1 heads. Pistons have marking on bottom DRP60 25443. Can you help, what pistons do I have?

 

[33 IMP]

Just guessing here...Diamond racing pistons? Give them a call with the etched five digit number. Looks like a job number to me.

 

[zyzzyx]

Stick an endoscope down the plug hole to verify. You can buy one for your
smart phone on Flea Bay for about $15.