interchanging 55 pontiac chieftain trunk lid onto 57
 

Found a pretty solid 55 chieftain trunk lid for my 57 chieftain. Seem like the fit is there.:) The lock hole is in a different position. Will it work? Any modification to be made?

Maybe!
 

You should be able to use the trunk lid as long as you're car is not a Starchief.
Starchiefs use a longer trunk lid. Chieftan and Super Chief use the shorter lid.
KK

For anyone else that needs a Chieftain trunk lid 1955 - 1957 Chevy is the same any can be bought new.