Headlight / Grille questions

I have a 1998 Chevy Silverado, but I prefer the GMC Sierra grille stylings better. I have the new (used) grille shell with the turn signals and marker lights in it. I want to swap it out on my truck this spring when I do some other body work, but I'm thinking about updating the headlights and signals with new items (any number of options found on eBay). The problem I've run into is that some of the headlight options say they are Chevy or GMC specific. So, my questions are as follows...

1. Are the headlight openings in the grille shells different sizes?

2. or do they mount into the radiator support differently?

3. Are the signal/marker lights different between Chevy and GMC models?

Any assistance on this would be greatly appreciated. I'd like to purchase the items I want and have it all on hand and know what issues I might encounter before I tear the truck apart. Thanks in advance.

Dave

I would check with a scrap yard with these mod questions.