I got a brand new set for my 85 truck with 318, beat 12" of the #1 tube flat and still would not fit the chassis. flowtech = junk IMHO!

I would go with a hedman set myself.

I have 2 sb sets for my 2 trucks and a set of the 79250 bb truck headers in my 88 440 truck.

it has been said b body headers fit the d series truck chassis with a slight trim off the frame top edge for clearance.

I would be looking to see if the hedman 79250 would fit in your b body.

I bet they will fit because they don't need the trimming in a truck chassis so should fit in the b body engine bay with room to spare maybe.

not sure what the hedman part# for their b body is.