well, to close the loop on this-- I spent an hour or so trouble shooting the issue w/ novak over the phone. They agreed that the rad was the culprit, and that the shroud was sitting too close to the cooling fins. I gave them measurements for clearance between the front of the motor and the fans on the rad, and they redesigned the rad so that the shroud was sitting about 1/4 inch or so off the cooling fins. they sent me the newly-redesigned rad, along with three all new spal fans -- 2 are double the cfms as the old ones, the third is a few hundred better (the third sits in the center of the rad, and due to clearance issues had to be shallower than the other two). AND, to boot, they second-day aired the rad at no charge because I told them I wanted to get it installed last weekend.
Anyway, I installed everything last weekend, and it stays ice cold-- in the driveway in the sun at 90degrees outside idling with the a/c on, the motor actually cools down enough that the temp drops below the 180 trigger temp for the fans. No more issues on the highway -- even with the winch and license plate reinstalled, coolant never goes above 190.
Anyway, kudos to novak. Really stand-up vendor. The rad/shroud/fan setup I bought from them was worth every cent I paid for it -- if you're doing a 350 conversion, I can't recommend these guys enough.