Most people delete the IMRC's on those years anyway. All you need is a set of 4.10 gears and you will have counteracted the IMRC's. The Mark VIII computer is really going to screw you up. It has so many electronic items on it that you will get check engine lights out the wazoo. Another option is to wire in an RPM window switch to control the IMRC motor.Just make sure you have the computer from the 97' Mark 8. If you don't you wont have fulll potential over 3k rpm.
The heads on the 97' have two intake ports and the second one only opens up at 3k rpm. So without the mark 8 computer or some kind of tune it would not work.
Yeah, the pre 97 intake sucks a big one. The stock GT tune will run the engine just fine with the IMRC's wired open or gone, or closed. So, once again, if you are dead set on having the IMRC's, then wire in an RPM window switch.I'm doing the same kind of swap, but I'm using a '94 Mark VIII. Get everything you can from it. Computer, throttle cable, hoses....
The Mark intake will work, but it's a pretty poor design. An SN95 cobra intake is your best bet, but they are kinda hard to come by. A lot of people shorten the runners too on these.
I'm pretty sure your stock GT tune won't work because of the IMRC running four valves instead of two.