Greetings and Salutations. I am an "FNG" so please bear with me. I am going to be purchasing a 1990 F350 (Diesel- NATCH!) for my business. Aside from the fuel line replacements, are there any other replacements needed or suggested; i.e. seals, etc?

Anything made of rubber that touches bd on a regular basis and your fuel filter during the initial bd adjustment period.  You may need to change the fuel filter multiple times during those "early days".

Do you happen to know if the new replacement engines for the 7.3 have the new type viton seals in them or are they still nitrile rubber? My time is the main concern and I may very well go with a replacement engine to save it.

 I hopefully will be getting my setup going soon, and an f 350 dually is availble from a friend at an actual affordable price, so what kind of "conversion" needs to be done on this truck.  I have been studying this for a few years, but under the Volkswagen TDI concept as well as the other european cars that don't really need any converting.  I heard that Fords have the rubber stuff that needs to be replaced with something else...but what.  Is there a conversion kit or somethings I just need to buy for it.  Let me know.  Help a noob out, I saw some post about F 250's but maybe you guiys can tell me if there is a difference.  Thanks