It's gonna be a lot of work, the engine will fit in the compartment without spreading the shock towers I think, might need spread a little. I think that the swap could be worth it but, you have to weigh the cost of doing the swap, then consider finding a '65 with a 260 or a 289 arleady in it, then adding a 302 or 351 to that if you wanted., I'd go the second route if it were me, enjoy your 6cyl '65 but, still look for a V8 car, and if you find it, sell yours and buy the other, it will be cheaper in the long run, unless you can find good Ford 9" rearends at a junkyard, otherwise they'll run up a bill alone if you have to buy 1 from couurie or moser.