Hey Tom,
That was me. Do you know the year of the car that your pump was pulled from? I went to a website where they sell rebuilt IPs, and they seem to lump them into 77-79, and 80-81 for the non-turbo 300D.
The pump from my '77 has 350 on the plate nearest the firewall end of IP, and my '80 had 375.
My mechanic is going to put on an IP he has from a '79 300CD and see what happens. He said if that doesn't fix the car then he is not going to charge me for any labor associated with the removal and installation of the pumps. Fair enough I thought.
So at this point, even if it isn't the correct pump, it might let him know if the IP is truly the problem. If it was/is, and I end up needing a correct pump, we can go from there.
My mechanic I believe is doing me right. If it takes care of the problem, great! If it doesn't fix it, he is out the time of his labor, and I'm still just out his very fair diagnostic fee, and he will keep looking.
Can you take a close up of the plate closest to the shutoff end of the IP. That is the plate with the 350/or/375 data.
And by the way, thanks so much for the effort of digging up the pump and photo-ing it. I may still need it, I'm just in a holding pattern until I hear something more.
**edit**I just read the link I provided, and see that your IP is from and '80. Duh... That would be correct. I will let you know something when my mechanic lets me know something. I'm very appreciative!
May need IP for '80 300TD