As long as they WORK... and work well... i'd try 'em. I'm not concerned about legality. I like that they're bloody light too, being bias... unless ov course that comes at the cost ov reliability on the street/daily driving. I wonder about that. They're almost TEN pounds lighter...
If you aren't concerned with legality or using bias ply, then look at American Racer (formerly McCreary) IMCA spec tires. they offer a variety of sizes in both metric and old school alpha-numeric format along with a variety of tread patterns. Street stock d.o.t is where you might start:
http://www.americanraceronline.com/tires/dot-street-stock/Also look into Towel City Racing Tires. They offer competition retreads built on d.o.t. carcasses that are available with our without tread designs. They also offer cambered surfaces on some sizes. Dirt track tires with tread may be the starting point with these. They also offer pie crust cheater slicks for the vintage guys;
http://www.towelcityracingtires.com/racing-tires/dirt-racing-tires.aspxThe rub with both of these are they are designed as competition and spec track tires, so buying as a freelance driver might be a bit tough unless you can convince them you are an outlaw racer. They have policies about not selling direct in order to avoid cutting out track operators who make money off of track spec tires. You could always see if they have a distributor in your area and buy through them. Upside to both, they aren't expensive and they will out grip any standard street tire.
