Thanks Jeaton and Simpilot,
I found a photo of a -5 serving in the same action in '69, a top pilot's plane that's preserved as a standing diaplay today. The tires look either smooth profile or circumferential, it's hard to tell, but they're definitely not diamond pattern... It was probably mix'n'match, as you say, it was a time of emergency, El Salvador was getting planes under the table, any way it could in the weeks running up to battle, and during the action too, so they probably came south with whatever tires they had on when they were bought.
I'll go for the circumferential tread if I can get it, that should be reasonably accurate. Also, I can get a -1 cockpit from True Details for only $7, it's the -1/1A cockpit and the only major difference for the -1D would be the drop switches for the underwing load, and the fuel selector for when drop tanks were carried instead of bombs. That's a very minor difference, details a milimeter across and I wouldn't even know where to look for them, so I'm inclined to forgive the discrepency and save the $13 difference on a cockpit set that features those bits.
Here's another question -- the kit is designed to feature dropped flaps. What colour were the edges of the flaps on Corsairs? Dark red in 1950s USN fashion? Interior green?
Thanks again, and I look forward to posting WIP pics,
Cheers,
TB379