Limited number of donors out there for the W/S - my hunch is that the Olds is a [name redacted) and that it has been circulating for a while.
That would lead me to believe the roof would be either a '62 Bel Air or '61 Impala sourced part. Alternatively, and it would be a huge PITA, a dedicated builder could swap a styrene roof from the Bel Air (my vote for most likely) and stab the glass in.
Path of least resistance for the chassis / interior would be to find a janky '63 JoHan Starfire and sell off the body/chrome. Far from a drop in, but close enough for a shelf model.
Alternatively, Olds shared frames and rear axles with Pontiac from '61 on (had been sharing axles since '57.) Thus, a '61 Moby or '62 AMT Catalina would be a reasonably close donor, might have some boo-hoo with the front suspension which was a Pontiac exclusive.
Interior - your guess good as mine - if you have the IP, you could just use the custom from the '62 Pontiac, or, sand off the detail and re-scribe to match the '61.