I'm running Gatorskins on a pair of 27" Weinmann concave rims. I'm pretty sure they're hookless.
I run them at 100 PSI and haven't had one blow off yet. I weigh about 186 lb.
I bought several pairs recently and found
Bike24 had the best prices for quantity, even with international shipping.
Edit: Continental Gatorskins in 27" only come in 27x1 1/4" and have a wire bead.