Chris, from what I've seen of US Navy/Marines carrier aircraft tyres, it looks like the earlier ones were smooth, treadless, as on the early Avengers, and then changed to treaded, normally block or diamond. I think I have seen SBD's with grooved treaded tyres, but if your's is early, which I guess it is if around the time of Midway, then it's more than likely the tyres were smooth.
As for the interior of the gunners position, I'm fairly sure there were some colour pics in that walk around sequence on the web-site i mentioned in one of your earlier posts, either here, or in that other thread. Sorry, can't remember what it was called without looking at the post!
BTW, the interior looks great so far. That clear instrument panel will probably be a pain to paint and detail though.