What headers for s.b stroker in Early-A

IMO, OH YES! Even a mild 400+ cube engine can step up.

If the tti's didn't jump up in tube size, they wouldn't be that good. IMO, I think the 1-3/4 would be a min. for that size engine and anyone working up a 400+ CID engine would for surely want a 1-7/8 tube.