Oil pressure relief valve pistons

[Mark Ennis]

I am rebuilding a 2.7 MFI engine. I have carried out the oil pump bypass modification modification. Do I need to assemble with 2 new oil pressure relief pistons (solid ones with chamfer or just the one with the longer spring and piston guide and reuse the short one with the hole. Also there is evidence of corrosion in the walls of the piston channel. Is this a major cause of concern?