The K had all kinds of modifications done to it to incorporate the additional radio and communications gear. The turret front plate is different with a modified mantlet and added armored visor. The hull side plate on the right side has additional ports and antennas that wouldn't be present and the fender tools/gear were all re-arranged as a result of that. The K was built on M hulls complete with the exhaust and other arrangements/features unique to the M, so it's not really possible to backwards modify the K to an L without a lot of serious work.
Since you say you want an L with the escape hatches in the hull, you'd be better off IMHO getting the Ausf J 3-in-1 Smart kit as the "L" designation was applied after the fact to the longer-gun 5.0cm Js and what you describe fits to what is in that particular boxing. Plus you will have the added benefit of much better molding quality as the K is an Imperial series kit and needs a lot more TLC as a result. HTH!