We used the gapless rings for blown alky applications. The car seemed to mph slightly better but not enough to say the ring was a required component to win. What we did like was low measured leak and the ductile iron second that was essentially impervious to breakage. It didn't need the gapless technology to be ductile but at the time it was one way to get ductile second rings. Our top ring was a stainless .017 Dyke ring that was cerrtainly not gapless.
The two piece ring will flutter before a single piece ring will flutter. Thats probably important to the F1 crowd but not to a blown alky engine and certainly not to a Cobra engine at any rpm they will reach. I'm not persuaded they are an essential component in a engine build for a Cobra.
By the way having said all that, my engine has a 1.5mm stainless top ring and a 1.5mm TotalSeal gapless second ring with a high tension 3mm
oil. I did it not because I thought hundreds of horsepower were at risk, I did it because I've had 20 years of good experiences with the rings.
Like I said in my earlier post your molys are good rings and easy to seat. This won't be the last engine you ever do. Moreover you will probably freshen it several time just to try out different ideas and toys. Start with the moly and go up the ladder as your experience grows. No matter what you pick you're not loosing boatloads of horsepower.
Get the TotalSeal catalog (its a free download) and read the tech stuff. Knowledge never hurt anyone, even if it came with a little spin. Ignorance has hurt many. You don't need to buy their rings, you might want to benefit from their experience and research without spending your own money to discover the same stuff, the hard way.
Play with the available toys, decide what you like personally, hang your hat on it and most importantly enjoy your car. They really are a lot of fun.
Ed