I do not recommend 14.6 volts to charge LFP batteries. Especially with a converter that can hold this voltage for an extended period. Use the converter rating directly, no adjustment for voltage drop should be used.
I would avoid WFCO if spending money. The existing WFCO will not hurt the LFP battery but may not charge at the 14.4 boost level and simply remain at 13.6 volts. This will charge the battery fine but slower than necessary. Fine for the first trip or two if needed.
Consider a PD9200 series (standard, not the lithium)
https://www.bestconverter.com/9200-Series-Deck-Mount45 or 60+ amp is fine depending on the wire that connects to the battery is sufficient for the additional power. And the battery must be compatible with the full amp rating for charging. Some are limited to 50 amps.
#6 wire is good to at least 60 amps.