Radio questions and speakers

Id leave the factory radio in, and remote mount a modern head unit possibly in the glove box,
Also cant remember who but there is a member on here that makes a bolt in plate to go from one 4x10 to two 4" or 5" round speakers that way you can run a lf rf lr rr channel for each speaker, if you use the single speaker in the dash and three in the back with the two wire motorolla radio then you have to wire them in parallel, not the best sound quality but will play none the less, most of these cars radios are a single channel so if your using more than one speaker you have to wire them in parallel, its kinda a waste of time, i wouldnt waste your money on a retro sound radio or something that is a classic style modern radio, they are junk, have had my retro sound radio sent back twice now, if i thought about it i would of just hidden mounted a nice 100 dollar alpine or equivalent modern head unit and be done but thats my opinion