The 6th Digit.
'5' = Sedan
'8' = Wagon
For Buicks, the 5th digit also differentiates between:
'BN' = Roadmaster Sedan
'BT' = Roadmaster Limited Sedan
'BR' = Roadmaster Estate Wagon
'BB' = Coachbuilder (Limo/Hearse) Wagon
Thus, '1G4BR8' are always the 1st 6 characters for a Buick Roadmaster wagon.
1g1bl82p7rr127841 … Rust In Pieces, Rest In Peace …
They are NOT Lying to You
You are NOT Lying to Yourself
You are Being Lied to - BY Your Self
… Alone aka The Last Psychiatrist