I've had one do that corrosion thing before, and it does occur right about at the floor level. Since that part of the aluminum was different than the rest, you could definitely get some new to replace and you'd have to replace the whole length, but at least it isn't more than that. Your biggest challenge would be to get the 90 degree bend.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR