73-80 to 81-91 Front End Conversion

[JCampbell]

I've heard inconsistent smatterings of rather ambiguous info regarding the need to modify the front frame horns when dropping a 81-91 front clip onto a 73-80 truck.

I always thought said conversion was, for the most part, "bolt-on" (aside from notching the cowl for the hood hinges). What's the deal? Do the frame horns need modification, too? Anybody have pics? I'd rather do it now while I have a bare frame sitting in the garage, than fight with it later.