To the best of my knowledge, there is no interchangeability between SB and BB fuel pumps, right?

I think you will find that the big block pump has a longer arm.

WHICH big block?

The small block pump is the same as the 348/409. The Mark IV and Gen 6 are different and will NOT interchange with the small-block pump.

WHICH big block?


Gen1 SB and MkIV BB.
And that has ALWAYS been my understanding. BUUUUUUUUUUUUT, I have never physically placed one pump up to the side of the other block just to check for myself.
The question came up in a conversation and I just wondered if maybe there was a pump interchange that might not be aware of. That's why I asked.

The pump bodies are identical, but the arms are a different length and I would assume probably a different ratio as well.

Thanks everyone, that's what I thought.

Why is it that when you know something is true, you allow someone put doubt in your mind when you know better in the first place???????

This is perfect timing. I just sold an NOS that was on my SB and was kicking myself that I should have saved it for the BB conversion. I feel much better now!