Hy 52-Mobil,If the 261 came from a standard four speed truck the bellhousing from the 216 should fit and work. As far as I am aware there was only one year of 261 production 54 which used a six volt fly wheel, so chances are your 261 will have a 12 volt flywheel which will require a 12 volt starter. You can always compare the two engines components to check for differences, hope that helps.
