I've seen opinions over on Speed-talk that you only need a single but doubles sell.
Smokey Yunick used stock GM gear drives that came in HD trucks...Grumpy Jenkins used GM sets with the nylon top gear to get rid of bad harmonics in the valve train that killed valve springs.
Yunick also filmed the timing chains thru a clear plastic timing cover. He said the timimg chain at speed looked like a snake trying to escape from a small box....wiggled and whipped around
I'n a race motor long term wear isn't a factor so a single row would be fine.
Double rollers were never around back 40/50 years ago. I never stopped racing because double rollers had not been invented yet.... Can you imagine the first Indy 500 in 1911 being postponed because the SBC had not been invented?
