50 degrees? Not sure where you get your weather reports but I hope you're not paying for them. Lol. Only going to be 29 degrees in Syracuse on Saturday.
We use the same size reels for wireline and downriggers when fishing for kings. We use 30lb test for riggers. I believe it's better to have a little more reel than you might actually need especially for bigger kings. We use the newer model Daiwa Sealine 47 line counters for those applications. If we're fishing only browns we go with the Daiwa Sealine 27 line counters with 12 to 15 lb main line. I'n not sure how the 30 and 40 Saltist reels match up with the the 47 and 27 Sealines as far as line amounts for each model.
I'm not sure where you do most of your trolling, but keep in mind that what is working on the West end of the Big Lake might be something altogether different that what is working on the East end of the Big Lake. I would ask advice from those who fish in the area of the Lake that you fish most of the time. Water temp, water clarity, current, etc... all have something to do with it. Half of the fun is figuring it out for yourself