[ktwizza]

A couple questions on the speakers in this truck. It's a 92 xtra cab SR5. The front are 4" and the rear speakers are 5.25" correct? Also what is that computer chip looking thing they are hooked up to?

 

[Rycam]

All this has already been logged into speaker-fit data bases that you can access @ crutchfield.com or Best Buy or even your local car audio shop. The circuit board looking thing you refer to is more than likely a "crossover". This device allows only those frequencies to the speaker, that the speaker can actually reproduce.