Bought a "complete" 68-70 B-body body plug set from a reputable source BUT seems do have some extra while others are missing. Not terribly concerned - I can buy the missing ones. However, I'm puzzled by some of the larger ones - there are three types which all seem to be the same size. Wondering which ones go inwhich holes. The one's on either end are rubber, the one in the middle is plastic. Thanks.

I dont know the specific locations but the flat one, to the left, goes in the trunk. Its flat so the trunk mat doesnt sag into it.

The thick rubber one to the right goes in the floor. Rubber because they are durable and wont melt from the exhaust system like plastic ones would.

The plastic one, those go where the old one came out