That is correct
THE CHRA WILL WORK ON EITHER TURBO, THE ONLY DIFFERENCE IS THE COMPRESSOR TRIM IS 55 on riviera and 60 trim on regal, the turbine housing is the only difference, the compressor housing are exactly the same, just different turbo adapters with the riviera using the U bend and the regal using the little short funnel.
IT WILL NOT BOLT UP TO A REGAL BECAUSE OF THE EXHAUST SIDE IS MODEL SPECFIC
THE TURBINE HOUSING ARE ALTOGETHER DIFFERENT, YOU could use The chra ON A REGAL, THE CHRA ( central housing rotating assembly) some catl this the CARTRIDGE, will get you out of a jam, THE THROTTLE BODIES ARE CLOSE BUT STILL DIFFERENT PART NUMBERS, one reason being the hot water line connectors may be pointing at a different angle.
IF you buy this turbo, I would buy the U bend and the exhuast turbine housing from you if you are willing to sell it.
THANKS , REGARDS TURBO E38