Unreported Traditional IRA Basis with a Roth Conversion, Two Questions Options

[MSDalt]

In 2003, I rolled a 401k from a former employer to an IRA. I neglected to account for roughly $1,000 in after-tax contributions when I completed the 8606 for that year’s after-tax contribution to my IRA.

In 2008 I converted a portion of my traditional IRA to a Roth IRA and would like to be able to benefit by not being taxed on the appropriate portion of the unaccounted after-tax contributions from 2003.

Should I just include the additional amount of the after-tax contribution as basis in the calculation or do I need to amend my 2003 return to modify the 8606 from that year?

Is it too late to modify a return for tax year 2003 if there is no change in the amount owed or refunded?

Thanks.