Need help with ID of this coil

[mecnix1]

I have a set of ignition coils that came off a Chevy Avalanche, not sure of the year. Trying to get that info. Anyway the numbers on the coils are this.

 

12558693

H6T55171ZC

 

I was told these are LS1 Coils but when I ordered my replacement plug ins for my wiringharness, well they would not plug into these coils. Trying to figure out which parts are correct and which are not.

 

Any help would be great.

 

Thanks

[mecnix1]

Also, are there any other Gm coils that are better than are direct plug in coils over the LS1 coils.

 

Thanks guys

[99FLHRCI]

Google says 99-07 GMC Sierra 1500 among many others.