If I told you everything I know about this stuff, I'd have to start another website. I have masses of reference gathered over several years, to help me build this car (which I haven't yet). But here are some observations - a few pros and cons off the top of my head...
• There is no ideal Gullwing kit in any scale by any manufacturer. But at 1/16, there are the Minicraft and the Italeri (hard to find and expensive). Both have their strengths and weaknesses, and my build plan is to moosh them together. Do not even consider the sucko 1/12 by Renwal, Revell and Monogram (until I start putting mine on eBay). They make Barbie cars look like museum-quality models.
Minicraft has:
• A better body shape, while Italeri front fenders are too high and bulbous. But you'll need to deal with more flash on Minicraft, and both require proper body surfacing. With the exception of the opening parts, Minicraft has a single-piece body, while Italeri has separate front and rear lower valances.
• Minicraft has more accurate seats, but Italeri has a more accurate interior, including a chrome luggage rail and proper door upholstery missing on Minicraft.
• Italeri has far superior engine detailing.
• Either way, you'll need to devise your own method for door lifts (maybe 1/24 working shock absorbers?) or choose between down doors and up doors.
• Italeri has proper retaining lips for opening hood, doors and trunks, Minicraft has none - you may want to add some Evergreen strip (no big deal).
• Minicraft has an accurate space frame, which is the hallmark of the Gullwing, plus the underside belly pan. Italeri has neither.
• Minicraft has chrome wheels with separate beauty rings to provide for many accurate wheel variations, and the Italeri wheels are too large and clunky.
• Italeri has separate chrome trim for windows, grille and scripts/logos. Minicraft has molded-on window frames, and would require sanding off the grille mesh, and has incorrect script with only gray decals for trunk and dash trim. So it's a BMF deal with Minicraft.
• Minicraft has a more accurate stering wheel.
That's just a top-of-my-head basic overview. If you can't find the Italeri Gullwing to add detail to the Minicraft, you can get the cheaper and more available Italeri Cabrio (roadster) for the chrome badging/scripts and a better engine (and not much else). You'll still need to add detail to the Minicraft Gullwing interior, though.
For a good build analysis by the late, great Martin Swire (who had warping problems that are not typical), go here:
http://www.freewebs....55merc300sl.htm
If you're really interested in building a Gullwing, the Minicraft may be the best, but Italeri parts can add a significant improvement.
I'd go ahead and get the Minicraft kit (pay no more than $45 with free shipping) and check it out.
Until then, I remain your humble servant and stand by to answer any further questions.