The difference is RoHS and insulation material manufacturer.
HIF3BA-**PA-2.54DSA(00) : Not comply with RoHS(discontinued)
HIF3BA-**PA-2.54DSA(71) : Complies with RoHS, Sabic(discontinued)
HIF3BA-**PA-2.54DSA(63) : Complies with RoHS, Toray and our standard product
** stands for number of contact.
The same difference applies to the product names where the "DSA" part of the product name is replaced by "DS" or "R".