One of my first ever craigslist buys was some aftermarket sheetmetal . I got 2 doors ,2 rockers ,2 cabcorners , 2 oem style floor supports and 1 passenger inner rocker for $225 . I get them home and discover the paint the guy put on them peels right off , they smell like his dogs have been peeing on them and to make matters worse they are absolutely the worst stampings I have ever seen . One of the cabcorners I was gonna throw away ,the bottom flange tappered from 3/8" to 3/4" ,the skin was choppy and talk about over size . When I test fit it it over the old cabcorner it stuck out past the back of the cab a good 1/4 ". Like I said I was gonna throw it out and then it occurred to me that if I had to fabricate my own cabcorner I wouldn't have done any better . So I hammer and dollied it smooth ,reformed the flange and rolled the back curved edge to get rid of the extra 1/4" .I 'm very happy with the way it turned out. I guess what i'm trying to share is sometimes you have to "make it fit" .
P.S. all cabcorners are inexpensive so you might as well get the better ones .