Just realized my copy of the hand drawn part list doesn't have the last two columns shown there...lots of useful data cut off for some reason. So Jack, thanks for all the work making good copies available, and Lee thanks for the head's-up!
Steve listed the following collector gasket # some years back and it looks to be still valid: ROL EG24154. The disadvantage he noted was the bolt circle is a bit small - - - I *think* c. 40mm bolt circle radius is needed for an easy no-fuss fit so this would require some modificaiton.
Trying NOT to go there I ended up going with SCE 4203, all-copper type - good bolt circle size although the main diameter is a TAD smaller than optimal. (Might loose a HP or two due to that....) I can't find 4203 in the SCE catalog on line (!) now but it is still listed at Summit Racing.
I wish Pantera style donut seals fit the Mangusta design. The stock Goose parts might have lined up perfectly but I had to work at getting the flanges more-or-less parallel with all the new 'replacement' parts fitted