I believe the following to be correct; If not, I'm sure someone will let us all know fairly soon:
Check the side of your enlarger's lamphouse. There should be a plate that tells you what type lamphouse you have.
If it says Lamphouse D you have a D2 enlarger, won't have a 3rd (4-11/16 inch) variable condenser and will require the 3.5 inch two condenser set for your 80mm lens.
If the plate says Lamphouse DV, then you have (the newer ) D2V, which means you should have accomodations for the variable condenser, and should have a 4-11/16 condenser in addition to the 6.5 inch two condenser set.
Either way, if you're missing something, probably the only place you'll be able to find one new and quickly is through Harry Taylor at Classic Enlargers Its probably going to cost a few bucks, however.