I like 'em- in fact I now have two somewhat similar bikes- a 79 world sport- see thread in lightweight Schwinns and now an 81 World Tourist.
http://thecabe.com/forum/threads/1979-world-sports-gets-a-new-lease-on-life.93171/
The frames really aren't that heavy. I'd lose the outer chainguard rings which are rusty anyway and replace the fixing bolts with some $5 alloy from China- the cranks were really the best feature for their day. I'm a fan of Dollar General Chrome paint, that pretty well matches unpolished alloy and it can do wonders on semi-rusted components and hardware- albeit not miracles, but works well especially on derailleurs like those, particularly if they have rough textures that better hold the paint on. Use some solvent like WD-40 on the rust first- much of the light stuff will come right off, and then steel wool if not, and just paint over anything left. I put a lot on with a brush I spray first into the can lid- The hardware paint up well- but won't stand up well to much wrenching, but you can touch it up with a brush when it's on, and it's better than wax I think at keeping rust off then- works great on any derailleur road rash especially- you can fill in the scrapes with the right artist brush.
Replace the drive train otherwise- the chains and freewheels and they should become nice bikes- I've personally always dropped the huge Schwinn metal pie plate spoke guard from the get-go, but that's the old racer in me I guess- usually rusted anyway, and not needed if you know how to adjust derailleurs.Are the rims alloy?- if they are I might put some nice 1 1/8" inch tires on, or if they are steel, convert to 700c and run some 25, or even 23mm tires and you'll be rolling better than most people will ever know, and with a very noticeable weight loss. Cheap lighter upgrades are the seatpost- one piece post and clamp are now going for $10 on ebay- anodized colors! A $6 allen key seat binder and you've removed all kinds of heavy metal, Oops I see center pulls- some people like them- I like to replace them just to lose the hangers and all that metal! Nice alloy brakes can be had for $20 a set- again anodized if you look.
http://rover.ebay.com/rover/1/711-5...0001&campid=5335809022&icep_item=400224572309 The reach of these brakes isn't listed so ask about that first- this is just an example..
Add lightweight aluminium skewers for 2-3 dollars and really a great weight savings over steel vintage. Otherwise you can paint the skewers or hunt matching vintage skewers on ebay- and they are overpriced and not the value of modern ones, if authenticity is some hangup otherwise. Much lighter pedals can be had in the $15 range and I just got a nice lightweight vintage style rat trap with an alloy cage for the World Tourist- hope to post some pictures soon!- NEW and for less than the going rate for old used steel rat traps- Other pedals that deviate from tradition can save even more weight.
Colorful cork handlebar wrap is only a buck or two from china, and looks and feels GREAT, since the Schwinn plastic tape wasn't used on these originally, but I believe there WAS such a baby blue color in plastic if you care to wild hunt it down and pay much more.
Frame paint? a toss-up I think - paint is getting so expensive- Don't discount acrylics though- they won't last by themselves- but they are easy to mix to match a frame color, and then they can be clearcoated to hold in place. Keep much solvent OFF of the existing decals but clearcoat them if you want them further preserved. Good luck pealing off those stickers and licences!