Weren't 500 efi heads just 088s? You can find them in swap shop or pbss. I sold 2 sets this year. Expect to pay around 1k for a bolt on ready set

Casting number is 12562934.

you want this one

Thanks sutphen. I just found one at summit. Problem is the 2.25 vs 2.18 valve stem area. Can this be machined? I wanna re-use valves.

934 is the same as 088.

Dont reuse your valves with new replacement heads ...... False Economy.

I see most shop install guides with an air hammer ..... If you look in the guide bore after you remove the old guide , there is usually some deep scoring in the bore . I ream oversize with a Serdi for a round straight hole . I always heat the head to around 300 in an oven , dunk the guides in some liquid nitrogen . They will damn near
fall in , I have a mandrel that I insert in them and tap in with a ballpeen. They make product called Fluid Weld , I get mine from Goodson , stuff works great , couple drops on the guide and drive it in .

Even if I replace them I will still want to keep commonality with the other engine. As I understand it replacement heads have different stem diameters. Will ask machine shop if they can be opened to be consistent with other motor. Don't want these things to be all mis matched. Same goes for push rods. Will likely have them deck it down to keep push rod lengths.

your talking valve diameter and yes,,these heads can be opened up to except a 2.25" valve.merc does it and so do any of us that needs to replace a hp500 head.

i don,t want to sound like a debby downer BUT,if one engine needs replacement heads,why not the engine next to it that runs the same amount of hours in the same water.