Try this
alter PROCEDURE SP_TRUNCATE_AND_RESTORE
@CustDetails dbo.TempCustDetails readonly --User Define Table
AS
BEGIN
truncate table dbo.TBL_CUSTDETAILS
SET IDENTITY_INSERT dbo.TBL_CUSTDETAILS ON
insert into dbo.TBL_CUSTDETAILS (identityCol1, col2, col3)
select identityCol1, col2, col3 from @CustDetails
SET IDENTITY_INSERT dbo.TBL_CUSTDETAILS OFF
END
GO