Pick my converter?

Loaded question at best, lol! Buy the highest quality converter you can afford, but my gut instinct says 2200 rpm HD towing type converter, being your cruise speed at 60 mph is going to be in the 2300 rpm range. I am not going to recommend a brand because it’s a different world from when I’ve used off the shelf converters. I would talk to PTC or Ultimate converter to get their recommendations. I would ask more what to stay away from if I wasn’t able to justify the expense of one of their converters. If you haven’t already, put an auxiliary transmission cooler in front of the radiator and plumb it in to cool the fluid after it passes through the internal cooler in the radiator. Don’t be worried about over cooling the transmission fluid. I have never had a transmission failure from overcooling a transmission, but I admit to having burned plenty up plenty of transmissions from overheating them...