What??? 62/66 GMC grille swap - doesn't fit???

[GMCMG]

I hope this hasn't already been discussed, and most likely I am just figuring out something everyone else already knows.
I am swapping the grille off my 62 GMC (chrome) for another GMC grille I have laying around. I think it was from a 66 based on the letters, but I bought it with a bunch of stuff that was a mix of Chevy/GMC and probably varying years.
Just so it wouldn't look like crap, I shot a quick coat of paint on it (that really brought out the dents), and was all ready to bolt it on when I discovered that none of the holes line up. The mounting brackets on the back of the grilles are apparently different between years? News to me...
Recommendations? I am pulling the chrome grille to protect it, as the 62 is more of a worker bee, and the 64 will be the queen (one day many years from now). The chrome grille isn't perfect, but it's a darn good driver.
Can anyone offer any suggestions? I have these options: a painted grille from the 64 (assuming it bolts up); a grille from a 66 Chevy (probably the same issue as this one); drill new mounting holes; cry and put the chrome grille back on. Also, as my 64 is in pieces so I cannot check, will the chrome grille bolt right up to it?
Anyone got any good ideas/info?

[creep]

The other grille looks like it lays flatter than the chome one. Maybe its from a big truck.

[creep]

It looks like you might be able to drill out the rivets holding the headlight mounts in and swap them between grilles.

[GMCMG]

I hadn't given that much thought, but the guy I bought all those parts from did have a couple of bigger trucks; I got a set of doors off him from a big truck (way less cancer). I didn't realize the grilles mounted differently between the pickups and big trucks.
I hate to remove the mounts from the chrome grille, so I may see what my options are. I could steal them from my chevy grille, or just put the chevy grille on it, but I really like the 4 headlight look.
I just helped my father-in-law pick up a 1960 C60 from WI; it doesn't have the grille, so I could lay my grille on it and see. I'll bet you guys are right.
THANKS!

[jonzcustomshop]

Can't tell for sure, but the lower one looks like a big truck bracket, the big ones had a flat mount, and the regular trucks had an angle mount (viewed from the side) to them.
you should be able to just drill the rivets and switch the brackets, the grille itself is the same 60-66 and all sizes