GM piston # help

Could any one help me ID this pistions.. They are GM# 3876884 and in an early dated 69 427. I have only look at them through the botom of the motor (thats how I got the number).

Thanks, Dave

Showing for 66-69 427 car engine:
3888327 LH std
3888328 RH std
3888342 std
3888344 .030 OS
For 68-74 427 truck:
3893251

Possibly the casting/forging number and not the PN.
Check the tops.