Service tax in civil job

Dear Sirs,

In Civil job  ihat will be benefit in below cases :

1]If we charge Service tax on 100% basic Value in our invoice on customer. Can we get Input credit

2]If we opt composit method of charging Service Tax. i.e 40% of total value in our Invoice

3]If we charge only on exact Service value in our Invoice.

Regards,

Bhalchandra Ramdasi