whats needed for 97 civic to swap b18c jdm

hey guys my friend just got a 99 b18c (jdm)for his 97 civic coupe. my question is, can he use his existing wire harness (on his civic engine) or does he need a gsr harness? we've already got the rear si mount from honda....just kinda concerned about wire harnesses and wanted to ask the pro's in here!!! and if you guys no of any more problems we may have like injectors, distributors, ect. please let me know!

thanks in advance
hatchman