every headunit will connect to the original wiring connectors, they come with the adapter harness ready to plug and play.
define best? the best depends on what you want and how much money you have.
the best for me is probably a Pioneer DEX-P90RS, although an ok second choice would be DEH-P9800BT.
gibbons who are blinded by the alpine fallacy would probably prefer an Alpine DVA-9965R, or an Alpine DVA-9861Ri if you're on a budget. bless them they havent got a clue.
those who dont mind awful menus and mainly want a very sexy looking bit of kit (you know, the shallow people among us) should seriously consider a JVC KD-AVX33. bargain prices and will always make passengers say "oooh posh".
menus are a little awkward but you can create your own visualisations which is cool and it has a USB function and 3 outputs for 3 amps
(and its better made than a pioneer)