The dominant car in the 9800 series was the plugged-door reefer. They were "traditional sized." The plugged-door reefers were not standard "0" and were made, I believe from new tooling beginning in 1972. These were the first new cars made by the "new" Lionel.
I believe there are sixty-four (64) of the plugged-door reefers (including the two Cracker Jack colors) ... and they represent, IMO, some of the most fun trains Lionel offered in the '70s. Production of the 9800 series plugged-door reefers went from 1972 - 1986.
I haven't checked recently, but I seem to remember that there were no more than a half dozen or so of the Standard "0" cars (box+gondola) were made with 9800 markings. None had plugged-doors.
I have accumulated the entire run over the years. There were seven cars introduced in 1972-73 (9850, 9851, 9852, 9853 x 2, 9854, 9855). I bought each of them from Schmidty's Trains in Santa Clara, CA, for between $4.95 and $5.95 each. That was a major stretch at the time - even over quite a few months. 
A major favorite - certainly until Atlas introduced their reefers. 
