FITS:

1937-1962 Straight 6-cylinder - 216 and 235 CID
1957-1962 261 CID

What about 1954 to 1956 261?

If it fits what it claims, it could have simply claimed: 1937-1962 216/235/261

If anyone buys one for $29, please tell us how it works and what size/year engine you have.