Depends on if you are on a budget. For some of that stuff it can get real expensive going for name brands, but cheap if you don't care. This applies to items you didn't specify brands for.
Test pipe- Ebay has them all over the place. Never bought one, so shop at your own peril.
MSD- Ebay again. I got my 6A for $150! It's the most basic one. You better look on their site for the right model for your needs. It depends on what you are going to do in the end with the build-up.
Camshaft- I've got the Nismo R4 from courtesynissan.com for $300 and that's the best price for a new cam that I've seen. PDM racing has regrounds that require machine work on the cam towers, the half circle pieces that hold the cam in, and you have to send your old cam in, so in the end the price isn't all that cheap anymore, However, I do hear good things about their #404 cam. My cam's idle is very lopey and there is less power under 3000 rpms, after 3500 it comes alive all the way to red. There also is an R6 cam made by Nismo. I think I would like this one more now that I've ran my R4 for a while. Not that I am complaining, I just hate it sometimes in slow traffic at low rpms.
R4 is here:
http://www.courtesyparts.com/nms/s13/s13_1.html
R6 is here:
http://www.nissanparts.cc/catalog/?section=324(half way down the page.
Underdrive pulley- I wast thinking to do this next.
http://www.rpmoutlet.com/aspimp.htm#nissan
Electric fan- Best pricing can be had with a custom job from something out of the junkyard. Or a universal type from some place like jegs.com Doing both underdrive AND elec. fan will result in lower spinning alt. and increase elec. draw from it, so watch it. May be problematic.
ECU- Seems Jet is the cheapest. Check their site.
That's all the opinions I got for ya. Don't take my word for it. I did some research before purchasing those parts, but this will get you started.