structural biology - What is the distance between the 3' 18s rRNA (the Kozak consensus sequence) and the A-site of eukaryotic ribosomes during protein translation?

Kozak consensus sequence (KCS) is present near or overlapping with the start codon. I am not sure what you mean by distance between that and A-site. Start codon is localaized at P-site at the time of translation initiation. Distance between start codon/KCS and A-site at initiation is same as distance between P- and A- sites (I guess ~20Å). A-site keeps moving during translation and hence the distance keeps increasing. Crystal study is available; See here.

See this figure from the abovementioned study for the relative positions of start-codon, P-site (exit) and A-site (entry).