Well Scottmech, I don't know what expectations you have as far as car count, but I can relate my experience with a similar race we have up here.
My local track started a nostalgia drag race about five years ago. It started as a one-day race and became so popular it has grown into a three-day deal. A local FED/altered enthusiast convinced the track to have a FED/altered Nostalgia Comp class. This year there were nine cars competing. Our rules - no electronics, .400 Pro Tree, half second indices, quarter mile, qualify off your r.t.s. It is a $50 entry fee, $900 purse ($500 to win/ $200 r/up/ $100 semis). Our format is gambler's race or test-n-tune Friday (all classes eligible), and separate races Saturday and Sunday, each with a chance at $500 for a $50 entry. If you pre-enter both Saturday and Sunday you get to test-n-tune Friday for free.
I talked to the track manager and expressed my concern that our entry fees are not even covering the payout and I was worried that they might end the class. She assured me that the fan interest was high and they will keep the class because it is so popular.
I get my old Logghe car out for this race and a couple of other vintage events each year. My take is there are only a small number of car owners that have a track worthy car to do this. Most modern altereds (and a few FEDs) are set up for Super Pro with delay box/electronic shifting, etc. and are not necessarily interested in changing their cars to meet the rules for a class that is typically paying less than half of a typical Super Pro weekend payout. Others in the area are of the "exhibition run / cacklefest" mentality and not interested or not able to actually compete on track. And, yes, we had cars like that on the grounds that we just couldn't convince/ cajole/ badger them into joining us. Go figure.
So if you can convince the track that this class is a useful/ desirable component of Nostalgia racing even with a relatively small car count and is one the fans will embrace and, more importantly from their standpoint, come back to see next year, then you will have a realistic idea of what you can expect. One fan came up to me last year after I had just run a AA/A 7.50 car in my six banger E/A 10.50 car and said that was the
BEST match-up of the entire weekend.
Here's a seven minute video of this year's race. Enjoy.
https://www.youtube.com/watch?v=lG6tOzJHOdw&feature=youtu.be