I'm going through my project car and need to replace bolts and hardware here and there. For example, I need to replace the bolts that mount the fans to the radiator, where and how would one figure out the correct bolt size? Such as pitch, length and what not? Don't really want to carry radiator into a hardware store to try all the bolts, but ya gotta do what ya gotta do.

http://www.2gnt.com/CAPS/main14/main14sub010.html

Look here. Find the part number, look it up online, order them.

Not really going to help with length, but you may be able to figure out the other dimensions with the thread restoration kit from autozone:

http://m.autozone.com/loan-a-tools/thread-restorer-set/oem-thread-restorer-set/391372_0_0/?location=

It only has a handful of metric sizes, but you may get lucky.

Just go to the bone yard and get them for nothing.

I've got SS bolts from Lowes in the fan mounting points on the radiator. They are M6 1mm pitch. Essentially all of the bolts which require a 10mm wrench are M6 1mm pitch. I've replaced most bolts in the engine bay with SS. Essentially all of the bolts which require a 12mm wrench are M8 1.25mm pitch. Hardware store M8 bolts will take a 13mm wrench. That covers all of the cosmetic type bolts (OEM bolt with 4 on head). If the OEM bolt has 7, 9.8, or 10.9 on the head, it takes a significant structural load. Don't replace those with SS. SS is actually pretty weak mechanically. If you demand a greater variety of bolts than the hardware store can provide, try http://www.mcmaster.com. They are my go-to source for anything weird.

Corbin
'97 GSX dressed like a '95 ESi

You may have good luck at your local Fastenal, as well. I've gotten all sorts of weird stuff from them and if it's one or two units, sometimes they'll just give them away.