So I just installed some Rockford Fosgate Punch P132 3.25" coaxial speakers in my dash. The dash cover won't fit over them, I can tell you that much lol. They sound good though, built in crossovers. Not sure if people just put tweeters in to fit in the dash but not much room.
Also in my doors I put some old infinity Kappa 5.25" coaxial speakers with external crossovers(came with the speakers), Although theyre 5/25" they were too big, I cut my door sheet metal to fit them.
So all front speakers are 4 Ohm, which I left them bridged which they seemed to be bridged at the wiring harness that clicks into the radio, theres 2 sets of wires same colors coming together and crimped in the same connectors.
So with them being bridged still they should be at 2 Ohms.. hopefully if there are issues the radio will trip thermal over load.
How else can you wire them without maybe adding some 2 ohm resisters to bring the ohms back up to 4 ohms for the radio?
Last but not least I installed some 4x10 to 6x9 adapters from amazon, they were like $11, I needed to use the spacers the speakers came with otherwise the adapters would be touching the speaker surrounds. I installed some Polk Audio DB691 's which are 3 way 6x9s, they sound so good, great amount of bass almost like subs, I'm tempted to install a amp for them lol
My head unit I bought was is a Pioneer DEH-150MP Single DIN radio, it works nicely for what I was trying to accomplish, but I think for a little more money I could have gotten a radio with 10 more watts RMS, which would probably power the speakers better although they sound very good!