If you are removing them, replace them. The Explorer valve springs were underperformers and weak from day one. They served Ford's intended purpose for the engine, but only barely. Yours have 20+ years on them at this point, and they don't get better with age. Replacing them will even help the stock cam get a little higher in the RPM range before floating, basically a must if you upgrade to anything else.
I'll second Bigmatthew86's recommendation. My springs came from Alex's Parts many years ago. They no longer offer the kit I bought, or I'd share the P/N. Contact them with whast you have and your plans, they'll recommend which springs to get.
I haven't used the Trick Flow kit, but it seems to have good reviews as well when used as a replacement for stock application. If upgrading the cam at the same time, get what ever the camshaft or maker calls for and recommends.