How can a person give an iron-clad 100% guarantee where there are running production changes with many different components? And maybe some parts are drop-shipped that he won't ever see. He's probably had his head chewed out 100 times by customers he 'guaranteed' fitment in the past.
If they have the part, maybe you could take measurements from your engine block and ask if he can hold a dial indicator to the heater part, and maybe that's the best you can do. If I was the vendor and some items were drop shipped dealing with the general public, I wouldn't throw out many guarantees either. A vendor's just asking for their neck to be cut off. You might be a very diplomatic and understanding person, but some customers can be real ba$terds and go off the deep end. (been there)
I know it's frustrating. I go through that a lot too. But usually things work out ok, esp if ya did yer homework, which it sounds like you've done. The other option is to order it from your dealer and then you can hold it up and check when it arrives (before you pay). Sometimes dealer prices can be very competitive. They need to maintain sales targets too. Esp smaller market dealerships, ..I've found. Ask the parts guy if they'll give ya a discount and get as close to an online price as possible. Might surprise you. Worth a phone call perhaps.
