What do you mean by "data pickup", GA? Are you talking about which devices on the aircraft send data to the FDR and QARs or are you talking about signal processing/recording within the FDR and QAR?
I can see great variations between aircraft and FDR/QAR types here. Do you have a preference? There is no point us directing you to a site (if there are any) which talks about solid state FDRs when you are interested in non-solid state (tape type) FDRs, or optical QARs when you are more interested in magnetic QARs... or a site which discusses how EIU's gather such and such data, when your aircraft doesn't have EIU's
Rgds.
Q.