Will 400-455 headers fit a 350 in my 70 a body
Not worried about the headers hanging a little low just clearing everything else

 

Why do you want to put BB headers on a SB? If you all ready have them, just try them for fit.

 

It depends on the how that particular header manufacturer routes the pipes. Every header design is different. BBO headers are designed to clear with a BBO. The lower deck height of an SBO doesn't just make them hang lower. Shifting the pipes lower and more inboard can cause problems with hitting the crossmember, motor mounts, oil filter, and starter.

 

I used the Chinese stainless full length headers, BBO headers with my Olds 358. The passenger side fit perfect. The driver’s side hit the motor mount. I had to heat and bend that tube. The later style mounts would have probably cleared. After moving the tube, I could only fit the most compact mini starter.