Best I can say is the historic boats that used to have booths at the Cleveland or Detroit boat shows.
I'm sure the Donzi guys have one helluva a show every year - I believe in Cinci or Cumberland, and they would welcome anyone else with a "period"boat.
Aside from that, I got nothing.
Buckeye Lake has an In Water Boat Show every year with antique boats. That's the home of the oldest Chris Craft dealership so lots of old 'woodies" show up. There is usually some "classic glass" as well. Pretty cool stuff.
Went to a antique outboard show at Lake June in Florida this fall. They also had some neat stuff on small boats.
The OFF event on the Okeechobee waterway was awsome too. Again mostly lake boats but Still Crazy was there. Those boys did a great job with that.
To answer your question... no. Never saw only offshore race boat show. But... HORBA and Charlie Mc are doing just that and one better with there events See them in action and not on display.
Every summer we have two vintage boat shows in the Lake St Clair area. The most historic show is at the original Chris Craft plant in Algonac Mi, the other is at the harbor in the city of St Clair on the St Clair river. Over the the years most of the boats have been wood classics but as of late fiber glass boats are making there way to these shows. Here is a pic of my friends glass Fino classic. This Fino was built at the Magnum plant in Florida in the early 70's. This Fino has now has gone under a two year compleat restoration. Here are a few pic's of the restoration. As good as it looked in red & white, it's new dark blue & white color is just outstanding.