So I just picked up a 1994 f350 crewcab 5 speed powerstroke with a dead #8 cyl and I'm looking at used motors. I had really good luck with the last used motor I bough that had 125K for $500 but not having such good luck finding another cheep used motor this time around.

I found a 94.5 psd at a wrecking yard for $675 but it had a fire under the hood, they claim it was not engine related. My question is what besides the wiring and all the fuel and oil lines fuel bowl could be damaged by a fire? If I were to buy this one do I need to do a total tare down and replace all the gaskets? What other parts can be damaged? Valve guides, injectors, gaskets???

Bought mine with having a small fire under the hood. Mostly centered around the fuel bowl harness. I believe this may be somewhat of a common problem for those who don't maintain their trucks. If you have two motors then you should be able to make one good one. I would replace all gaskets, o rings and seals while the motor is out to make it easier. A little piece of mind. Will all depend on how hot it got and how long.

Have you determined what's "dead" about the #8 cylinder? Might be less work to address that, if it's something simple / top-end.

no compression, we pulled the valve cover today and the valve trane is in tact however there appears to be some milky oil-water near number 8... So maybe just a blown head gasket but we wont know till we get the head off.