Just to tie this thread off, 15777 was definitely the right hose part. I just had to cut it down to size. It was a PITA to access and messy with coolant flowing out of the block even though I had already drained the radiator. The old hose was badly blistered, gummy, and clearly about to burst. Lastly, I just soaked the original hose clamps in some zep degreaser and scrubbed with a toothbrusher and they were as good as new. I'll work on changing out some of these other hoses over time.