Tim,
I am in the process of bring a 72 280se back from a long sleep in a barn. Hopefully I can add some insight.
Here is a link to the electric fuel pump. That's the best price that I found for a new pump. If your car hasn't been converted to the new style pump you'll need a bracket and 3 isolators. The new style pump has an extarnal fuel return to the tank. Putting a tee in the return line at the tank is not a problem. However I found that the return check valve in the injection pump is different if the late style pump bypass is used. I understand that the you can just leave the bypass port on the electric pump plugged if you have the old style pump in the car now and don't want to change the return check valve. There are used pumps out there but to me a used pump wasn't worth the risk.
http://www.europartsdirect.com/epc-items.asp
I also found out that the gas tank in the MFI cars is quite complicated. I was able to get a metal stripper in town to clean out my tank. What a difference. Attached is a link to the Pagoda group. Their tech manual will help you understand the fuel system.
http://www.sl113.org/wiki/Fuel/Start
Hope that helps. It sounds like you have a fun project. Be sure an post pictures.
Charlie