/6 A727 id

I have a A727 removed from a mid 70's truck with the following markings on the DS pan rail "PK 4058384-7326 3034". The case body has rough cast marking "188-1" on both sides of the bellhousing (mold markings?). I have found reference to a A727-RG but it included the comment that "an adapter is used with it". I personally removed this trany and used the running motor and there was no additional adapters/parts. Anyone know anything about this beast? Yes, I know the A904 would be a better match but we expect to run max boost.