Even the TYC's are hit and miss. All comes down to variations not only in the new headlights but also in the original truck, as none of them are exactly what you would call blueprinted as they roll down the assembly line. As someone else mentioned I've seen crooked (droopy) factory headlights on a one-owner, never-wrecked truck. Kinda freaked me out as I fully expected them to be some aftermarket junk; nope, Sylvania GTE housings on original brackets.
On my black '94 C2500LD I had to knock the locator dowels off the TYC brackets in order to get them straight/level in the grille opening, slot the bolt holes on the brackets, and then open up the "clearance" holes in the core support where the screws on the backs of the housings go once you start turning the adjusters. Took a bit of jacking around to get them to fit well. On the maroon '94 C1500 they fit a little bit better (knocked off the locator dowels, but didn't need to slot anything) but it's a different truck and a different set of the exact same headlights, bought at the exact same time...
Richard