When we did my 216 - 261 conversion
Read about it here, we just moved the ring gear from the 216 flywheel to the 261's flywheel. We flipped the gear around while we did it to put the unworn side of the teeth to the starter gear. Swapping the ring gear was pretty simple. Why didn't we just use the 261 flywheel as is? I don't remember.... maybe I talk about it in the writeup. Or better yet, maybe Jerry remembers -- he was there guiding us through the whole thing.
IF you are fortunate to find a 261 out of the 1954 mold (again, see the article...), its a FAR simpler swap than the later 261's. Either way, make sure you know what year your block is so you get things right (like main bearings). Knowing the Date Code is critical, not just the casting code as not all 261's are identical and you want to know exactly what you have before you starting buying expensive parts for it
How do I know this? Indeed .... read the article
