Local rules 466 single charger diesel or 410 single intercooler or 370 alcohol and i think 310 twin? Anyway if a person ran a deere 404 with cooler what head would a person run? John deere old fat injector head??
55 series head with stock 404 bore won't work......unless you notch the sleeves for the valves.....and even then, the question is what benefit is the larger valve/flow when you are shrouding the outer edges so badly. This head obviously will work great if running 466/7.6L.
Yes, the 6.8L engine has a nice bore stroke combo, but finding the head with the bolt on box type intake is very difficult. Your next issue with this engine is injectors. They are not the standard KDEL type so it may drive up the cost on modifying them.
It would involve moving valves. I’ve not personally done it, but I do know of engines with 55/7.6 heads and bores smaller than 4-9/16 that run real well
