Well for 1500 bucks plus shipping, I think I'll pass. (I can buy a good TIG welder and plenty of aluminium to practise on for that kinda money..............) 
You want thin wall Aluminium Tigger, Terry? I'm your man. Just speak your immigration blokes and send me the ticket. I'll work for board and lodging.
PS My missus asks if she can come along too.
PSS Don't worry I've already said no.
OK mate, you're on, come on over and teach me how to weld ally and I'll get you a job here, done deal! Leave the "ball and chain" back in the old dart, as good as she probably once was, she's past her prime and there's plenty of nice women here, and if you'd prefer one a little more "British" than Aussie chicks, we can order one cheap from New Zealand, Kiwi chicks will do anything to escape the pointy headed, buck toothed, cross eyed, sheep shaggers of "Middle Earth", ha ha!
Back to reality for a mo, I've got an alloy GS/GSX swingarm here, I thought about making some custom swing arm bushes and fitting it to my CB750 endurance racer project, but it's 3 inches longer than the OEM arm, so (unless you're building a drag bike or a hill climber) it's pretty useless in the real world. I thought about shortening it, but it'd be a lot trickier than cutting a couple of inches off the arm. You'll also have to slightly narrow the shock mounts, they're too wide for CB750 shock clevises.
Staying in "realityville" for a few more minutes until the drugs kick back in, there's nothing much wrong with the OEM swingarm. I run a 140/90 - 16" rear tire on my K1 with no problems so unless you're just a "form over function" type, you can install a tire bigger than you'll ever need for the fiercest CB750 racer (most of the post classic racers here in Oz don't go any bigger than 130's anyway, as it makes the steering too slow) with no problems.
The standard arm is a great design, it's already a "box section" so a lot less "flexy" than Kawasaki and Yamaha's offerings from the same period, is not heavy, and is easily "braced" as there are very few "appendages" getting in the way.
You've got a choice of the standard K1-k6 arm for drum brakes, or (my preference) an F2 arm for a rear disc setup. I'm going to install a spare F2 arm on my K1 so I can use the 18" WM5 Borrani rimmed rear wheel with trick cast iron racing rear disc and Bridgestone BT45 130/90-18 rear tire. I think I'll get it chromed first though, I always liked chrome swing arms on CB750's............... Cheers, Terry.
