Here's a few photos of the rear-bend snorkel and S-tube I have. I acquired them separately, they did not come from the same car. FYI, the snorkel was repainted (badly), but the S-tube is still wearing original paint as far as I can tell.
The OD of the snorkel measures a bit over 2-13/16" (don't have my dial caliper handy), taken near the root of the tube, not the edge which is slightly wavy. The S-tube is a nice slip fit over the snorkel, I'd say less than .010" diametral clearance.