I contacted the seller and got a bunch of pictures and screen shots of an article from 1985 where Shaw talks about his designs, including this one. The 32 Custom Pearson is a one only prototype. That boat is almost exactly like Pearson 40, only smaller. Same design. Shaw used this 32 as his personal boat for a while but his wife hated it as it was a typical racer with no amenities inside. Definitely a piece of history.
With all due respect, this explanation makes no sense at all. To begin with, the Pearson 40 hull and rig bear no relationship to the Pearson 32. The Pearson 40 predated the Pearson 32 by quite a few years, The Pearson 40 was a 'Whale body' centerboard boat. The Whale body design concept was a short lived IOR I rule beating strategy, that was quickly made obsolete by revisions to the IOR rule.
The Pearson 32 was a modification to the earlier Pearson 31, that was a classic IOR II design. The design changes to alter the 31 to the 32 seemingly were in response to changes to the IOR rule that took away the rating advantages of the fractional rig. If the Pearson 31/32 was a prototype for any other Shaw design my guess is that it was a prototype for the Pearson 37 which was similar to the design concept of the Pearson 32 but updated to better take advantage of the ongoing frequent revisions to the IOR rules of that era.
Looking at the pictures more closely, the hull on the 'Custom 32', the stern of the Custom is closer to the 31 than the 32. My best guess is that the Custom 32 was a 31 hull, with a custom deck and a similar rig to a 32. I raced a 31 and the 31 were not great boats. They were under canvased in light air and very squirrelly in a breeze. Putting a masthead rig in a 31 would have helped in light air, but would have made the boat worse in a stiff breeze. My guess has always been that the changes to the run on the 32 were to address this issue.