460 swap into 1978 Mustang II

None, that's a horrendously bad idea. The engine will not fit without major cutting and welding. The steering shaft will not clear anything wider than a 302. Everything would have to be custom made to fit... This will almost certainly result in the end of the 1978 Mustang that you're working on. Even normal 302 headers don't fit in a Mustang II. The car was originally not even made to fit anything other than a 4 cylinder and small v6. Ford had to revise the whole front end to shoehorn a 302 in the car in 1975.

From the article: "Ruggirello was reported to have spent $12,000 to have G&R build the car—huge money in 1975". That's 1975 money. Think about that. I'm guessing that you don't have the money, experience, or resources that those professional builders had to make such a car. The amount of work to replicate such a thing, make it look good, and do it right is way more than most anyone on this forum could even do.
A 460 has none of the benefits of a much smaller and lighter small block. Big, heavy, large displacement engines are no longer needed to make big power. Back in the day the term "there's no replacement for displacement" was often true but nowadays it's hardly the case at all. A good 302 build is realistically achievable here, this not so much.
It's your $ and time but I think this is a bad idea to start. As I said this would likely end badly for the car.