From your picture it looks like a 6 cyl distributer,
I can see the flange where it sits against the block
is higher like a 6 cyl distributor.
I looked in my Ford parts book and see that C4OF- B
is listed for a V8 but C4OF-E is for a 6 cyl, yours is
clearly marked B but may be a mis stamp.
All your V8 distributors should be the same length,
can you post a complete picture of the distributor?