Am I ok with this? KB107 in La block

First Yes as Dwayne suggested, use the same piston & rod in each corner
Second if you want to see if the rods a equal length & straight bolt two rods without pistons on one rod journal then line up the pin bores & see if a wrist pin will pass through the pin bores... (Assuming these aren't pressed pins... If they are pressed pins you'll need a undersized pin....
We use to use that method to check 6 & 8-71 rods... works well...