My mechanic neighbor has an F-250 with an aftermarket rebuilt 5.4 that dropped a valve. Heads are done, but google isn't much use when it comes to matching this piston.

Flat top reads: R5675 - 0.75
Under one skirt has 90L80
Under opposite skirt has CDHT in the middle, and T601 (Al type?) next to it

Or does this even matter, and he should just get any 0.75 over piston?

 

No such thing as a .75 over piston. The biggest you can safely go is .030. Those pistons appear to be generic TRW cast pistons. If he dropped a valve there is going to be damage to the rod also and possibly cylinder fracturing. I wouldn't attempt to swap a new piston into a engine it will throw the balance off if nothing else.

 

It's .75mm over, which seems to come as a surprise to those of us born before the 90's.

 

Okay .75mm is roughly .030 inches so it's at max bore, the weird part is the pistons listed are in inches and I have no part number to give you. I can say it's not a Ford reman as Ford won't go past .020 because of the reliability issues.

 

IT DOESN'T MATTER! It just matters what year so the piston top has the right configuration.

Your mechanic friend should already know that the aftermarket pistons are stock replacements and as such they weigh about the same as stock. So buy wherever he can buy a single piston.
In the Sealed Power line the part number will be HxxxCP for set of 8 and WHxxxCP for just one.
BTW, TRW hasn't made pistons for a very long time.

R.