Youll need to buy a manifold for it, and then get all the brackets, an intercooler, a beefed up fuel line. A new chip, and custom tune. A higher hood for clearance. All the air intake plumbing, probably an 03/04 radiator setup. Its definitely not a weekend do it yourself bot on. In the long run you will be $$$ ahead buy going with an procharger or some other off the shelf kit. Had the exact same swap done on a 99 cobra talking from experience If you go with eaton you can hope for about 430 rwhp and right at 400 ft lns on 98 motor depending on tune. You should go real easy on tune as the 98 motor is high compression, and you will be best advised to run 100 octane to keep it a ll together.
i was going to say it isn't worth the cost, but that last post pretty much summed it up. I think they go for 300 or something on ebay. would be nice though!