Guys, they are different. You need to take a look at the electrical connections. Some pumps have one and some have two and the type of connection is different. I have an 81 300SD with an 04 vac pump. Although I specified an 04 (this is the middle number) pump, SVMBZ@aol.com (a good company to source for used parts) sent me an 03 and it had two electrical connections. Would not work. I sent it back and they sent me an 05 but fortunately -although it was not the exact same size or shape as my original pump - the elec plug worked and the vac hose fit. So it worked.

My recc is to send a picture of your pump to the supplier and make it known how many electrical connections it has.