On the timing chain--yes, you will need a vintage-specific chain set as the 5.0L has a bit more clearance and thus allows for slightly thicker gears/chains. The 5.0L chain will likely rub on the back of the vintage timing cover. I'd suggest Cloyes true roller or equivalent (like Edelbrock) timing gear. Oil pumps are interchangeable from vintage to modern although you will need a vintage style pick-up.
You will also need vintage-specific bolts (available from AMK or others),a new 3-bolt 50oz balancer (like the one from Speedwaymotors.com), and a hardened gear on the dizzy if you use a vintage style distibutor.
Currently enjoying my grandfather-in-law's 1966 A-code coupe. I am the second owner. Ü