I wonder if you could get a 8' flareside bed from a previous generation and put 1980-1986 flares on it?
That would look better than the splicing that I see here.
The previous generations had 8' and 9' Flareside beds for F-100/350 etc. I think a 1973-79 8' Flareside bed would match the best. Although the 1973-1976 did not have 6' 1/2 Flaresides they still had the long beds.
Here is a link to a 1979 from Bring a Trailer. Could 1980-1986 flares fit that bed?
https://bringatrailer.com/listing/1979-ford-f350-4x4/
Truck: 1981 F-150 Explorer / Engine: 300-6 California MCU Feedback System / Trans: T-18 - 4 speed / 2.75 Ford Rear Axle Open Diff.