Hey Bob - I moved your post to its own thread to keep from hijacking the other thread.
You will need a LiFePO4 charger to fully charge the new batteries on SP. It is unlikely that your converter will have the ability to charge the LiFePO4 batteries properly. A FLA specific charger will only keep the lithium batteries charged to 60 - 70%, which is fine for storage, but you do want to charge them fully (100%) before boondocking. This can be done by the engine alternator through the BIM or BIRD or by using a LiFePO4 specific charger such as this 20 amp charger:
https://www.amazon.com/gp/product/B074X1QK2R
But if you leave that lithium charger connected you may overcharge the chassis FLA battery though the BIM/BIRD. You can install a simple switch in the control line for the BIM or Trombetta to disable/enable this battery bank connection.
Charging from the engine alternator can be a heavy load on the alternator charging the lithium batteries, especially if they are low to start. Replacing your current BIRD/BIM with a Li-BIM prevents overloading the alternator and shortening its life. It also helps prevent overcharging the chassis battery when charging the LiFePO4 batteries on SP.