Front shock dimension differences for Gen 1 and Gen 2?

I just replaced the factory Bilstein front shocks on my 2012 4X4 with 5100s.

A friend has a 2000 4X4, and needs new front shocks. I know there are different part numbers for the two different generations, but what is the difference in dimensions for the front shocks?

If the bolt dimensions are the same and the 2nd gen shocks are slightly longer, would they work like a shock lift?

I'd like to give him the year-old factory shocks, but not if I might be putting him in harms way.

Thanks in advance!