I wasn't really sure what this vehicle looked like so I googled "Mitsubishi 3000gt interior" [images] & found this: 1998
Unfortunately, the combination of deep seat cushions + buckles that are forward of the bight looks pretty much incompatable for most (if not all) child safety seats
Do you currently own this vehicle & are expecting a newborn
How soon? You may need to find a more family friendly vehicle
There may be a seat for this vehicle, but I don't have a specific definite answer -- I might have some ideas of seats to try, but ultimately you should take your choice of carseat to your local CPST for a hands on check (link in bottom line of my signature)