1981 300SD - I got sidetracked from tracking my door lock vac problem but am back on the case. You all say that I need a mityvac.

There are several versions of the mityvac on Froogle.com - 4000 series, 5000 series, etc. Which one should I purchase? I generally like to purchase slightly above my current needs just in case I need the tool for something more complicated in the future - so I am not looking for the cheapest version.

Thanks for the assistance.