Dhall, I don't envy you in the slightest.  I'm a mechanic for a small earthmoving company here.  At the front of our workshop we have a spare parts store.  I was helping out there a few weeks back.  One fella called in wanting a thermostat housing for a 3 cylinder perkins.  
I asked "What model Perkins is it ? "
dumbarse"I'm not sure, it's in a tractor"
me"Ok, what model tractor is it ?"
da"Umm I think it is a David Brown."
me"What model David Brown ?"
da"Ummmm.....I'm not sure."
me"Ok, without a model of the engine or tractor, there is no way I can give you a price or even any idea of what part you may need."
da"Oh, I thought all 3 cyl perkins would have the same thermostat housing."
me"-_- ....................Tell you what sir, if you can get me an engine number and the model of the tractor I should be able to help you."
da"Where can I find the engine number?"
me"stamped on the engine."
It continued on like this for another 5 minutes or so it seemed before I finally convinced him that he needed to get me some details on the engine before I could do a damn thing for him. 
