David S. Custeau, 63, of Plaistow, N.H., and formerly of Haverhill, husband of Rachel M. (Florent) Custeau passed away Aug. 16, with his wife by his side. Born in Haverhill, he was the son of the late Rudolph G. and Mary A. (Cashman) Custeau. Raised and educated in Haverhill, he was a graduate of