do you mean an adapter from a 3.9? if so...
from looking at it, I kinda think it would.
yes the intake tube is longer, but isn't the airbox the same for both cars which holds the MAF and is replaced by the KKM adapter, then the KKM would just slip on to either intake tube and then tighten the clamp?
I know this can be done for 1st gens because I machined and welded up an adapter to bolt to the OEM MAF holder (which on 1st gens just unbolts bolts from the air box) to allow an old K&n filter i had from a mustang. then after my 3.0 was totaled, I gave it to my cousin who put it on his 3.9. but I know that the two generations are pretty different in this area.
however if you are talking about an adapter from a 1st gen 3.0 going on a 2nd gen 3.0, then no, there are a couple of big differences.