Checked the site out for myself. They definitely need a new fluid dynamics engineer.

To toss out those Two numbers randomly 16 and 64 TIMES is insane. To many variables. If you were trying to pass the Whole Engines water system through a Heater Core, single, dual, triple, pass then it May be closer to the truth.

But the newer rads have a lot more flow capacity. But with that said, Yes, the dual; and triple pass rads will have more flow restriction, but Not Nearly the amount, the Stewarts web site suggests.

But, I will back peddle a little, the standard newer rads if big enough and with the right shrouds and fans are plenty enough to cool a lot of our rides. Lack of shrouds and fan placement is probably the biggest issues of poor cooling.

Dave, my Howe crossflow rad is a 19 x 31 for my A body. Had to trim some excess sheet metal from the driver side frame rail, and make a pocket in the passenger side front portion of the frame rail for it to slide in. So if your up for some miner fabrication you can go bigger on the rad.