Rep Power: 518

I'd urge you to research part numbers for various versions of the cars in an online Honda parts catalog

Here's just a few dealers with online catalogs, I'm sure there are many more and most sell online at wholesale prices

hondapartsnow
hondapartscheap
bkhondaparts
hondaautomotiveparts

.com/

 
Rep Power: 512

To make it nice and readable, here are the things you can interchange:

• 01-03 coupe/sedan: bumpers, hoods, fenders, lights, spoilers, and other body parts including doors, handles, etc.
• 01-05: engine/transmission stuff, just about any interior item, most suspension parts, wheels, brakes
• 01-02: front struts (crash bolt was changed from 14mm to 16mm in 2003)
• 04-05: you can install rear tail lights from an 04-05, but it requires a socket change or some MacGyvering for... I think the rear brake light. Or was it the turn signal. One of the two.
• RSX: shifter assembly (if manual transmission), engine if you feel like doing some work, rear sway bar, e-brake cable assembly (if doing a civic Si rear disc conversion), Front seats (one hole needs to be drilled out a bit). There's probably a lot more, but those were the common ones.
• Civic Si hatch: rear disc brakes (takes some doing, but pretty much bolt right in, but you'll need a different e-brake cable. 2002 retained the 4x100 lug pattern. 03-05 they changed to 5x114.3), front seats (one hole needs to be drilled out a bit), engine if you feel like doing some work (same engine as RSX, in fact). There's probably a lot more like the RSX, but those are the common ones.

Universal stuff:

• Wheels: as long as they have a 4x100 lug pattern and have an offset of +35 to +45, they should fit. 14-18 are common sizes people put on the 7thgen. 19s and 20s if someone was feeling frisky.
• Lug nuts: as long as they're M12x1.5 thread pattern. If you have OEM wheels, they need to have a ball seat. Most aftermarket is 60-degree conical. Honda Mugen rims have a 45-degree conical shape.
• Shift ***** (if you have a manual transmission): if it has an M10x1.5 thread pattern, you're good.