Answer to: LCD Replacement iMac 20"You can use suffixes SLA1 and B5 as a substitute for the SLA3. The A5K2 will not work. The SLA3 uses LVDS to communicate with the scaler card and the A5K2 does not use LVDS.
Answer to: LCD screen: iMac 20" 20 and IsightIt does not always have to be an exact match. For example, I have replaced a (SL)(A1) with both a (SL)(A2) and (B5). Both worked. Some other suffixes will not work though. You have to check the data sheets to see what the voltage level is and what type of video signal is sent from the video card to the LCD are.