[MKS427]

My two cents.
I considered a Coyote, but I wanted that sound. You mentioned 351W/427. If you go with 408, you can use a factory block, 427 is not really recommended. If you go with a Dart block, + $2,500, then you can go 427 up to 468 without restriction. Mild 408 about 500 hp $7,500 plus engine dress, MSD, etc. vs street performance 427 about 580 hp $12,000. If you elect to go for a big cam or will experience altitude changes, you will want to go with an EFI system. You will need to decide upfront, as the cam will be different for EFI.
Power brakes aren't really necessary, but that's a personal choice. Remember, bigger cams have erratic vacuum, especially a slow speeds. Ditto for power steering. I went with electric power steering, with a Saturn Vue unit. You can adjust the assist. However, it doesn't return when you let the wheel go. It is something I wouldn't do again.
Tires, wheels, and brakes. I struggled with this decision. I wanted the nostalgic look and the big brakes. I went with 17" wheels and big brakes. Both work well, so pick what you like.
Things you didn't ask about, but might want to consider. Make sure you get a heater/defroster. I added heated seats for the wife, pretty inexpensive. Second roll bar for the wife. Raydot mirrors, the stock mirrors are very ineffective. LED headlights, I have low cost generic that look like the Harley ones at half the price. 165° beam light up the ditches next to the car. Expensive sticky tires. I had Nitto R555, they weren't sticky enough for 585 tq, so I went to Nitto NT-01. Hugh difference! Air pressure will be significantly low than what you'd expect. Ask BDR, what they recommend. I run my 17"s at 22 psi.
Good luck and enjoy
PS: SAFETY! Watch some Youtube videos of people crashing their Cobras, not to be morbid, but to witness how quick things go bad if you don't respect the car.