460 swap into 73 Mach 1

The 71 Mustang was designed to fit the 429, which is externally identical to the 460. The 71-73 were all physically identical, they simply dropped the 429 option in 72-73. To install a 460 in your 73, all you need is stone-stock 71 429 parts.

Yep - what 2+2 said. I had a '73 Mach 1 with a 460 about 20-years ago. '71 429 parts are what you need; motor mounts & front springs for sure. I didn't have any cooling issues with the 351 2-row radiator (using clutch fan & shroud), but that was no AC, etc.

The real PITA was headers. I used a pair of Super Comps - well made but I don't see how any full-length header wouldn't hang too low on these cars. I hope choices have improved and there's a shorty option available.

If not already equipped, pick up a Trac-Lok 3rd member for the 9-inch. You'll need it with all that torque! :o)

Funnel

I did this swap in a convertible. I got my motor mounts from Mustangs Unlimited. The isolators from Autozone. FPA makes a mid length header. Mine needed a little tweak around the steering box. I used a stock replacement 351C radiator from advance auto and modified the shroud and fan to work with the 460. A performer intake with a drop base air cleaner will fit under a stock standard hood. NASA hood gives you a little more clearance. I used the stock FMX with a 351M/400 bellhousing. If you want to use a C6 you will have to source one from a 429/460.