Wow! I expected such a topic to receive much more of a flaming than anything so far.
So what you're looking for is a long-wheelbase 4X4 with a solid inline-6 motor, and reliable Toyota drivetrain... buying an FJ60 is alot cheaper than grafting a somewhat hard-to-find aluminum Rover body onto a frame that was never once meant to receive such a tin-can in the first place.
I'll list the potential issues:
- Electrical!!! Lets face it, Rover has a reputation for wiring that's about half-a-step better than something made by Thomas Eddison, and about half as reliable. Likewise, Toyotas have a knack for falling into the hands of booger-eating morons who thing that since they know the difference between wire cutters and their front teeth they can do who-knows-what to everything that resembles a wire.
- Electrolysis: aluminum body on steel frame with steel doors... there's a chance that any Rover you find that would be sold at a reasonable price would look like swiss cheese, and aluminum isn't as fun to weld as good ol' steel.
- Fitment. We all know that any F motor isn't exactly small. Shoot, they're tractor motors that Toyota first rushed onto the FJ25 assembly line because they were pretty much all they had. Can a rover body even accommodate a long, and tall motor? Do you know a reasonable aluminum welder who can make things fit, if they don't?
- Obscurity. Cruiser parts are now selling for a premium because it's getting harder to find many pieces necessary, shoot, you're pretty much AFU is you have an F135 needing a rebuild, and don't have a parts lot behind your house. The 2F's not too far behind. I blame the modern fascination with gorram V-pattern blocks. Top that with a body that's also hard to find parts for...
I'd love to see someone build a Rover up proper with something really groundbreaking, (like a 1PZ/R151/R1AF) but this whole idea just sounds... like alot of work for very minimal results.