Other then unique and cheap, don't really see any reason to go to all the work of modifying the firewall, fabbing up mounts, etc... Either a 289 or a 302 is going to be an easier swap, and will result in a car with much higher resale.... By the time you get the 300 in and mod it so it has some power your going to spend as much or more as you would putting a V-8 in.... If you go looking for a V-8, keep in mind the 289's and 302's are narrower and shorter then the 351W and as such would be the easier swap... Some of the early Falcons actually came with a 260 and a 4 speed....so things do fit quite nicely.....