That and the straight tail (obviously). They started out not being all that different (and ended up that way as well). The early 60's Debs and Bos both had IO-470s, The Debs had the 225HP model for most of the run (with an option for the IO-520/285HP in 66/67). The Bos until 1965 had the 250 or 260HP IO-470 and then moved up to the IO-520. After 67, the Debs just became the model 33 Bonanzas. By 1970 they'd given up on V tails entirely with the model 36 Bo.