Anthony,
I also have converted from 4-bolt to 5-bolt wheels (4-1/2" fronts and 5-1/2" rears). I did it on VW drums, changing the rears to '67. It wasn't a big deal, but like everyone says, there is an offset difference between the 4 and 5 bolt wheels. It is especially a concern if you are changing from 4-1/2 to 5-1/2 rim widths.
You can have the wheels "pushed" by a wheel shop (Stockton Wheel did mine). They cut the welds on the center, push the center to the new offset, then reweld it. Pretty cheap as I recall, about 50 bucks a wheel.
Some of the VW parts suppliers don't seem to know about the offset differences. Whoever you plan to buy the wheels from, make them actually measure the offset on the 5-bolt wheels before you buy them.
You can measure the offset on the wheels you now have. Then you can stick you head in your wheel wells and figure what the offset difference will cause.
If you are changing discs, there are disc set-ups that have zero track width change.
Tire sizes are not changed just because of 4 or 5 bolt wheels (of the same width).
And, you are right -- the 5-bolts look more correct, because they are!
Mark