Pardon my lack of diesel knowledge.  The intwerweb has not been helpful so here goes.-

I have a '78 FIAT ALLIS 545B loader. We were having fuel related issues, so I was on the hunt for a mobile diesel mechanic. Finding one for semi's is easy, older heavy equpt not so much. 

Mechanic #1 - informed us inj. pump and injectors needed a rebuild. Ok we have a place here that can do that. They inform me that out pump was actually in good shape. They resealed it and done. My injectors were in need of some help, also done. Mechanic reassembles. Thing ran but never quite right. 3 injectors pushing fuel thru the dust shields. (this is a condensed version), Happened  over the course of 6 months or so progressively getting worse.  Have no faith in this mechanic.

Mechanic #2 - (this started within the last 3 weeks). You need new dust seals, ok I get new dust seals. He also claims timing is off. Anyway fire her up, 3 dust seals ruined within seconds (another condensed version here). This has been a process, this mechanic does roadside repairs and doing mine between jobs. Ok I get that but....   

I get 3 replacement seals -yet to be installed.

So here is my question. Does this engine require copper washers/seals?  I have looked online at parts sources, 2900 injectors are shown without seals in the pictures. But I have found 3500 injectors and they are shown with the copper seals (go between the injector and the cyl head). In the pics the injectors look the same. Can anyone put me in a direction here? Thanks in advance.