A Gen V BBC bottom end is bullet proof. They all have a four bolt main bottom end with a one piece rear main seal; and there is no provision for a mechanical fuel pump (how you tell a Gen VI from a Gen V in the bone yard). Your friend wants new higher compression pistons (thirty over), rings and bearings and the bottom end is done.
If you are going with EFI then you will need to buy not only another manifold and MAP controlled port injectors, but an aftermarket CPU to control it. Edelbrock sells a system for the big block using a Victor Jr. intake manifold (a single plane), or a carb replacement self contained TBI. He could also buy the Arizona Speed equipment EFI that uses a tunnel ram manifold with a speed density equipped single throttle plate (similar to the old Gen three Camaro EFI TPI on steroids.
The TBI on the motor now is sitting on top of a low rise Rochester QuadraJet with an EGR valve in it. He could take the TBI off and use a Quadrajet to replace it. But only if he doesn't live in a state with emissions inspection.
Or you can replace the cast iron factory intake with a Edelbrock RPM Air Gap manifold and a 750 Holley carb. This still requires a new small cap HEI distributor; as the one it now is computer controlled (It also has a 5,200 RPM Rev limiter built into it, so it will never go any higher than that). This is because the heads he has now are flow limited to 450 horse in stock form and are done by 4,800 RPM.
Duration in your cam choice is determined by where you want to make power. If you want to spin the motor to 7,200 RPM then the distributor and heads say it won't happen. A lot of valve overlap (long duration cam) also says you are going to have a lot of problems with EFI. A carb is much more forgiving of a big cam choice. If he has to have EFI then you are limited to a short duration cam (under 220 degrees at fifty) ground on a 114 degree LSA with as much valve lift that you can get. This is known as an RV grind.
An RV grind might just be what he is looking for as he may be towing a house behind him as he travels the world. I don't know what he wants his motor to do.
Finally I agree AFR heads are a good choice just keep in mind the cubic inch limits they mention on their web site should be heeded as an intake port that is huge will kill any mid throttle performance. Oval ports are recommended for all BBC under 500 cubes. Rectangular ports work not as well as enlarged oval port intakes as the corners are dead to air flow. Brodix uses huge 440cc oval intakes on their biggest asymmetrical head.
Like I said I don't know what he wants to do with his motor. It could be the "Peanut Port" heads with pocket relief and short side radius work, adjustable valve rocker arm studs, and bigger valves might be the correct path. They will support nearly 600 horse when reworked.