Yeah, the rear trunk for a supercharger? That is an easy trade-off I think. I know TPC makes a
supercharger for the 3.4L for about $11K and they say it generates quite a lot of additional power (378hp at the wheels).
Of course for sinking $15K for a 3.4L and another $10K for the supercharger, it might just be worth it to sell the 98 and buy a more recent S for the better brakes and stuff instead.