89-91 Suburban Grill swap question

[LowRodder]

My question is about the core support.

I have an 87 that I picked up from the original owner. The grille, headlights, headlight trim, parking lights, and front bumper are all missing. I want to go back with a 88-91 suburban grill. Every thing that I've heard and read says that the core support must be swapped.

My question is, why ? Is it just so that the head lights will be an easy bolt up? or does the grille mount completely differently?

I am planning on cutting/modding the core support to make room for the 90's one piece headlight. I've seen a hand full of folks on hear have done it and I really like the look. So I'm wondering if I'm gonna be cutting out and modding the core support to make the 90's headlight work anyway, can I just use the stock 87 core support?

any help would be greatly appreciated. I'm gonna be order/gathering up a bunch of the parts this week.