re: pedals,
I also have 1-pc cranks on an old Schwinn (79 conti) and an old Iverson 3-speed. I have been using Wellgo BMX pedals w/ clips and straps, but recently discovered that airbomb.com sells 1/2" thread quill pedals for something around $15. Heckuva deal. Of course, this only helps if you are going with clips and straps, obviously you need to get an adapter for clipless pedals.
IIRC the 1 to 3-pc conversion thingy only costs between 30 and 40 bucks, can't remember the amount. For that much though, you could just buy a better frame with a 3-piece crank and in better condition.