I would go with 3.5 for customization and some semblence of balance. I agree the long stat blocks for 3.5 are tedious and annoying, so I often run monsters simply out of the book. Converting older material is not a big deal for me because there is so much written for 3.0/3.5. But for 1E material, there are conversions available for nearly everything. I quit playing during 2E, so I'm not sure what is there that you would want to use (I didn't like most of the 2E stuff and thus I quit playing during that period), but I'm sure there are conversions for the popular stuff.
In any case, the web is your friend. Find the on-line NPC generator, or the treatsure generator, or someone's conversion of something, or just an NPC in a free adventure or conversion and use that in your own stuff.