I took a look at the weight of your 2019 K-Z Sportsmen Classic 160QB trailer, and based on that you will likely be able to use the Dexter Trailer Springs Over-Under Conversion Kit # K71-384-00.
I say "likely" because this kit is designed for 2-3/8" diameter axles, which your trailer probably has, but we don't have any way of knowing that so you'll need to take a measurement just to be certain.
As for welding, it is a good idea to have the spring pads tack welded on in order to prevent... view full answer...
As the G345 key is a different pattern from the G344 key, it will not be the best replacement. What you need is the Global Link # 295-000070. This is a direct replacement for your G344 key and will get you all squared away. view full answer...