Umm.... The suspension and brake parts are different. They are W-Bodies and we are H-Bodies. The H-Body is stiffer than the W-Body, so we have a slightly different suspension in the back. If you look the strut/spring are seperate since the frame is stiff enough and we get a better ride from that, or if people have the air ride suspension. Brakes are similar but mount differently. Like I put Powerslot rotors meant for a 99 Grand Prix and it works on my Bonneville perfectly since its the same size and offset. Exhaust parts are a little bit different. This is where GM typically changes HP and Torque numbers through exhaust systems. Like the Grand Prix'* have a nast U-Bend for their O2 sensor after the cat, it'* not a happy site if you see one. Supposedly the downpipe/cat is different from Grand Prix'* to Bonneville'*, but this is Grand Prix guys saying it. It'* the same engine, just have to probably adjust it to make it fit. *&* Headers also makes headers and cat/flex pipe for the 3.8L. They don't list the Bonneville because we are H-Body and all the cars they list (Grand Prix, Monte Carlo, Regal GS) are all W-Body. So they all fit for them. But I am guess the exhaust can be made to work, it should not be that different, GM is not that ghetto.
Otherwise pretty much all the engine parts will work on your car.
ADTR 1999 Black Bonneville SE
2003.5 Yellow Mazdaspeed Protege
2003 Azure Blue Mach 1 Mustang