I have a D4 later book here & they list the same 5F6607 pump assem. for them & I kind of thought they did as things there are about the same on both the 4 & 6 cyl. engines except the D6 has two more cylinders. Did you try a Cat dealer for parts as they might stock them yet.Might be just as cheap to buy a whole new pump if available for them if they are eat up so bad with rust.
sj, we can't afford the canadian cat dealers up here, so that is why i posted on the BBs to find a southern source for pumps and parts.
also the fact a lot of new BB members can learn too.
thansk