I recently purchased a 90 ZR1 with 1,826 original miles. It has been through two NCRS judging events, chapter and regional. When judged, it had a service replacement battery which resulted in a 12 point deduction.
The deduction is not so important to me but, making the car as 'correct' as possible is. With that in mind, I had an original battery case restored and dated. Lastly, I found an original decal.
The cost of restoration was just under $800, including shipping both ways.
I know it's not for everyone but wanted to share, in the event any others are considering the same.
Regards,
Mark