i know you said the pistons are good but can u tell which one he has
I now have each piston revision for the Coyote GT.
The late '12 piston appears to be the same as the 11-12 piston except it has the phosphate coating. The '13 piston has the coating, the extra oil drain back passages, and the gas groove in the second ring land.
From top to bottom: 11-12 piston (03/22/2010-12/08/2011)....Late '12 piston (12/08/2011-02/27/2012)....'13 piston (02/27/2012-current):
11-12 piston:
late 12
13
Threaded Mode