Classic & Vintage - What's the upgrade path for classic drivetrain components?

I'd like to make my '81 Schwinn Le Tour a little spiffier....

The Bay seems loaded with uber-cheap Shimano goodies, but I don't know if a sparkly, newish 105 RD will drop into my '81 Altus set up. Shimano customer service says I need to stick with a 5 speed RD, but some here say I could be rocking a 6 speed RD with no problems.
A chain and RD are probably first up on the swap out list and then perhaps the brake calipers and pads and then levers.

I've searched a goodly bit and haven't found any info on parts compatibility/interchangeability.

some here say I could be rocking a 6 speed RD with no problems..

Why not rock 7s with no problems?

Freewheel: $20
Shifters: $15-20
Rear derailleur: $15-20
Chain: $15

I had assumed that 6's and 7's were almost interchangeable...... what's the advantage for choosing 7's over 6's???
I was leaning toward the Tiagra components I'd seen on The Bay. Any input on my choices is welcome.

THe advantage of going 7 over 6 is that you have one more gear. Plus, it's easier to get a super wide spread with a 7 speed freewheel than with 5 or 6.

Also, remember, if you stick with friction (I'd go bar-ends, since your'e upgrading everything), you can use any derailer with any crankset or freewheel, as long as it'll physically take the number of teeth you're giving it. I'd upgrade with 105 everything, if I were you.

I replaced the Altus derailleurs and shifters on my '81 Voyageur 11.8 with Ultegra FD-6603 and RD-6500 (long cage) and old Suntour barcons. I converted to a 700c wheelset with a Shimano 3N-80 dynamo hub in front and 105 in the rear with an 8 speed SRAM cassette. I used Tektro R365 calipers (nutted version) and immediately replaced the stock shoes with Kool Stops in the back and VO shoes in the front. I am very happy with the setup.

miamijim's advice is good if you continue to use the original wheelset.

Skip the Tiagra and Sora stuff. Look for all metal Shimano derialleurs, Exage, Z-series, 105, 600 Ultegra, they're all very reasonable priced. They key is to buy all metal parts.

I upgraded my Schwinn to 7 speed and went with early 90's Ultegra derailleurs and Shimano Indexed levers....Its my errand bike and it gets beat on; Never skips a beat or misses a shift.

THe advantage of going 7 over 6 is that you have one more gear. Plus, it's easier to get a super wide spread with a 7 speed freewheel than with 5 or 6.

Also, remember, if you stick with friction (I'd go bar-ends, since your'e upgrading everything), you can use any derailer with any crankset or freewheel, as long as it'll physically take the number of teeth you're giving it. I'd upgrade with 105 everything, if I were you.

Hmmm...
Good info thanks.

I had planned on sticking with a 5 speed rear wheel for the sake of staying simple/traditional...I hadn't thought about upgrading to a cassette either...

BUT - I did plan to upgrade to alloy wheels at some point- would it make any sense to stay with a 5 speed rear, or should I go ahead and update to cassettes and more gears(on the alloys)??

I'd like to hear y'alls thoughts and really appreciate the input.

I am interested in this as well, have a fairly cheap old bike that i want to make a little more pleasant to ride, but it is not one that i can justify spending more than about $100 on, thinking of brifters, going to 700c, etc, as these could be spares for any bike.....
Is it possible to go to 700c wheels w/o replacing the RD and cassette?

I had planned on sticking with a 5 speed rear wheel for the sake of staying simple/traditional...I hadn't thought about upgrading to a cassette either...

BUT - I did plan to upgrade to alloy wheels at some point- would it make any sense to stay with a 5 speed rear, or should I go ahead and update to cassettes and more gears(on the alloys)??

I'd like to hear y'alls thoughts and really appreciate the input.

I agree that the 105 route may be a better one.

can anyone help me out with the wheel question?