Classic & Vintage - Rear hub spacing?

I have a early 70s schwinn continental, and I recently upgraded to an shimano ultegra crankset. I will be buying alloy wheels soon, and my 5 speed freewheel is shot. What are my options as far as number of cogs vs. rear spacing? Will I be able to add 2 or even 3 cogs? If so, what would be a good cluster choice? If not, what 5 speed options would i be pleased with? Will I have to spread the frame? Will I need to purchase a wider hub when I get a new wheel, or will a lager freewheel thread on? So many questions......any help would be greatly appreciated here. Complete noob learning as I go....

http://sheldonbrown.com/frame-spacing.html

If you're getting alloy wheels (assuming these are used and freewheel compatible) just get a 6 speed freewheel. Won't require any change in spacing.

Thanks for the help.

If you're getting alloy wheels (assuming these are used and freewheel compatible) just get a 6 speed freewheel. Won't require any change in spacing.

Aren't early-70s Varsinentals 120mm?

If you're getting alloy wheels (assuming these are used and freewheel compatible) just get a 6 speed freewheel. Won't require any change in spacing.

It might, but not much. The Continental is probably spaced at 120 mm; 6 speed freewheels like 126 mm spacing. You can probably either just put a 126 hub in, or stretch the frame a bit as you do it. If worst comes to worst, you can bend (cold set) it a little to stretch the spacing. I put a 6 speed wheel on my Varsity and just crammed it in there, ignorant of the the fact that the spacing was a bit too narrow. It works fine.

I've cold set other frames, though, and I found that a good size C-clamp can be used to do the job. Put the fixed end against the inside of one dropout, and the foot of the screw end inside the other dropout, and unwind the clamp.

Yeah, probably is 120, but it's a Continental. Cram the hub in there and go.

Yeah, probably is 120, but it's a Continental. Cram the hub in there and go.

I don't like to go to the trouble of setting up a bike without paying attention to the dropout parallelism and general good fit to all of the parts.
So even if the axle spacing were to be kept stock, I still examine the dropout alignment visually, and correct if needed before proceeding further, espacially with these Varsinentals as they seem to more often be out of alignment.

Another consideration is that many of the bike-boom bikes with non-Campagnolo (and generally lower-level) parts groups is that quite a few 5-speed wheels already have room for even a normal-spaced 6-speed freewheel.
Just look for the humungous gap between the smallest cog and the inside of the frame dropout, and if there is more than 9mm of space then usually a 6-speed freewheel is a go.
An Ultra-6 freewheel usually works if there is 6mm gap (where a modern chain usually needs at most only 3.5mm of space between the smallest cog and the inside of the dropout).