most all head units put out the same amount of power. Everyone (OEM and aftermarket) chooses from the same library of 4-channel BTL power amplifier chips made by ST, Toshiba, NXP, etc. They're all approximately 16 watts RMS per channel, clean, into 4 ohms. The "peak" ratings some aftermarket head units advertise are unmitigated BS.
Now, if you have the Mach 460 system, your job is a lot harder. In that system, the head unit only powers the mid-tweeters; the woofers are driven by external amplifiers and you'll need some kind of integration kit to make them work with an aftermarket deck. Ford's line output to external amplifiers is/was some funky 250 mVrms balanced output, where most aftermarket line outputs are 500 mVrms/1Vrms/2Vrms/4Vrms single-ended.