I realize that this is a recently bumped thirteen year old thread, but that was so cool!!
I don't think I saw this discussion before.
I have magazine articles with a 1989(?) Grand Am based GTO concept car;
Mind you, back then the Grand Am was a cool car - about the size of a Sunbird, but much sportier.
I would have loved to find a nice 1989-1991 Grand Am with a five spped and the iron duke to swap SD-4 parts on to - but post 1988 2.5/5 speed Grand Am's alone were rare (even twenty years ago), so I ended up essentially buying, and fiddling with the production version of that GTO concept car;
A Quad4/5 speed Grand Am.
Interestingly, the last incarnation of the 442 was a 1990-1991 Quad4HO powered Calais - the Oldsmobile version of the Grand Am;
The production 1990-1991 442 was done absolutely like the 1989 GTO prototype.
1990 Calais 442 (full proper name: Cutlass Calais Quad442)
(please note, those are non-production wheels, the 1990 442 came with five spoke 14" wheels)
1990 Grand Am SE
The interiors were also light years apart.
All of this aside, a DOHC Super Dtuy "Iron Duke" is still something I'd love to do one day - but with the absurd rarity of the SD-4 parts, I'm pretty sure it will never happen.