Pretty sure the heads are different, The '98 will have "B" heads for sure and I believe the 2005 Aviator would have "C" heads. So to use the intake, you would need adapters or use the Aviator heads. Either way, the Aviator intake would likely not fit under the stock hood of the Mark VIII.
Most Ford DOHC enthusiasts will say the C heads are superior in flow and potential power, certainly if at least comparing stock applications. Whether or not you should really comes down to if it's for necessity or convenience and your level of determination.
You may or may not be aware that the preferred Mark VIII intake swap is the DOHC intake from the '96-'98 Mustang Cobra.
The intake for an Aviator is built for a truck and and well suited for HP applications, that being said it will not fit on B heads. If you swapped the Aviator motor into the Mark VIII, you would need a cobra/Mach 1 intake in order to close the hood.
I have an Aviator(ish) motor going into my 97 eventually and will be running the Eaton setup from an 03 Cobra.