Thanks, Cliffy B. If you're referring to what I think you're talking about, it's the retractable oil cooler. It's directly under the engine and would be just fine since it's well forward of the spray. If you're talking about those big things behind it, they're just exhaust fairings which were left off on the R-1820-powered Hawk 75s.
As for the differences between the R-1820 and the R-1830, they were both still very common at the time in the US Navy. The Catalina used R-1830s, so you'd find parts for those just about anywhere.
On the Swedes, I said "B 17", not "B-17". I'm a bit pedantic when it comes to designations, so I'm not likely to leave out the dash lightly.
Besides, the B-17 was R-1820s, not R-1830s.
This:
Not this:
For camo, that's your choice. You really have six options for the Swedes.
1) Historically accurate overall natural metal/dope, such as the scheme seen on
Swedish Harts pre-war and
Swedish Catalinas post-war.
2) Historically accurate polished metal and gray/green paint combination,
as seen on Swedish Hawker Ospreys.
3) Historically accurate green over gray with large numbers and national markings. It looks distinctly Swedish, you can't go wrong for wartime Sweden, but man is it boring.
As seen on about everything between 1942 and 1950, including this float-equipped S 17BS.
4) Historically accurate green over silver camo
as seen on the Gladiators and Harts of F19, the Swedish volunteer unit that served in Finland.
5) Historically accurate Italian 2- and 3-tone camo
as seen on Swedish CR.42s and Re.2000s. Now, the Swedes didn't generally go about repainting other aircraft like this except for the Severskys, but you do what you want.
6) Whatever the heck you feel like. The Swedes were generally boring when it came to camo. You want to do something different, go for it. It's your profile.
Cheers,
Logan