Two and 4 door frames are the same . As long as it is a 98 .
" Air ride " (air suspension ) frames are different as well as convertible frames .
88 and Super 88 frames are shorter .

Does or did you car have "Air ride " ? That may be why you think you have a non original frame . Many "Air ride " cars were converted to springs with a special kit sold by Olds dealers . After failures of the air suspension system .

The following is a rundown on what fits what ;

 

Thank you for the reply, Picture below of correct 59 frame borrowed from "joe_padavano".
The areas circled in red are not present. So the radiator support mount is missing.
The A-arms look like there to far back by an inch to fit under the inner fender well correctly.
The front spindles are disc brake and the front and rear bumper mounts are about 1/2" to narrow.
The rear end is a GM 12 bolt with 5x5 bolt pattern under a 4 link.
The rear body mounts on the kick up don`t line up either.
Not sure what the frame I have is for but its not for this body.


missing parts

 

Does your frame look like this ;



If it does , then it's a 61 thru 64 frame .
The 59 four door frame will fit your car .
Make sure to get a bill of sale and /or a title to the frame to prove ownership .
The VIN number is stamped on the frame . And some states or localities may also check the frame .
This is the same number that is stamped on the door post tag . The number is usually stamped on the outside of the right frame rail just behind the front wheel and just in front of the rear wheel .