1989 Excel pistons

[BQUICK]

Need to replace two pistons on 1988 Excel. Ones in it are 6K7 and have LP on them (light piston?) They have a short tapered pin. Look a lot lighter than 6R5 pistons I have. Anyone know if I can use the 6R5 pistons to replace? I am going to weigh them both to see how much lighter. Never thought the rotating assembly on Excel was different......
78 and 88 show 6K7 pistons while 89 shows 6R5 in the parts list.

[rodbolt17]

nope you must use the correct pistons.
over the years they have changed a few dimensions.
try using the sierra pistons.
they are also marked up and P or S. some simply had an arrow that pointed to the EX.