Re: frustration!! - Headers!
BB frame mounts sit the engine toward the passenger side about 3/4". I assume the drivers side is where you are having the clearance issue. BB stands should make more room between the header and the gearbox. If 2451 headers won't clear with the BB stands, I wouldn't think switching the to SB stands would help. Unless.... raising the engine would help with your clearance issue, then they might. I believe the BB stands also sit the engine lower. I don't have a lot of experience with headers. Can you jack the drivers side of the engine up some, hang the headers where they need t go, and lower the engine back down? I had to do that with my BB years ago when I was running headers on SB stands.
Experience...... It's what you get when you didn't get what you wanted.