For my application the signal output port(Pin 5&6) frequency range is from 1KHz to 20KHz, so according to Table7 & Figure 3 its working for 10MHz with L3=L4=0 i.e. no external component is required, only transformer is required for impedance matching. So, "will this configuration work for 1KHz-20KHz (much lower frequency) output" No information is available for such lower frequency IF output in the datasheet.
Sorry it's taken so long to get back to you, I'm just seeing this now.
The output of the LT5560 can be modeled using the circuit in Figure 10 on page 19 of the datasheet. Because the frequency is so low, the reactive components in that circuit essentially don't exist, so the mixer's output is basically just a 1200Ω resistor.
To match to 50Ω, you'd need a 24:1 impedance transforming circuit that will operate at the frequency range of interest. I think you'll have a hard time designing this with a standard surface-mount transformer. Instead, you might consider using an IF buffer circuit to drive the mixer's load. Examples of this can be found in Figures 21 and 22 on pages 24 and 25 of the datasheet. Note that these designs were done for an IF of 450kHz, so your blocking caps will need to be larger to work well at 1kHz.
Senior RF Applications Engineer