Hy dlhenk, A 261 is a bored out 235 basically, it was an old hot rod trick to put the head off of a 235 on a 261, it gave you a higer compression ratio, and hence more power. A 261 is the largest displacement engine that will "bolt in" where any 216, or 235 was, making them a much sought after engine for upgrade purposes, hope that helps.
