I run LS1 coil packs on my LS2. The coils and valve covers came from an 01 LS1 and were no trouble at all to fit to an 05 LS2.
The 2 main (coil group) electrical connectors are not different, but the 8 tiny connectors to each individual coil are different. The LS2 plug leads are L shaped and fit better.
Note: LS2 coils are much "taller" and will hit on some LS1 fuel rails.