That $625 part is only a small portion of what you would need to install it into your car. There are a LOT of expensive parts and fabrication needed to supercharge your 4.0 when starting with this.
Here is a more comprehensive kit that includes most everything you’d need except a bigger fuel pump…Notice it costs nearly $7000… withOUT installation.
And doing this to an old engine means you are likely to blow the whole thing up in very short order. I would not recommend it. Save up to trade it for a V8 or a later model Mustang with the 305 hp V6.