I don't think the lithium vs lead debate is all that clear cut - which is best for you definitely depends on your usage.
Lithium has a huge advantage when it comes to weight - a LiFePO4 pack weighs about 1/3 what a lead equivalent would. But the OP has a huge diesel truck, so weight is probably not an issue.
Lithium has an advantage with cycle life - theoretically you can get 5 - 10x more cycles out of an LiFePO4 than a lead acid, but in practice this remains to be seen, and often batteries are killed by abuse, not old age. Whether this advantage is worth it to the OP depends on their usage scenario. If you use the camper 5-6 weekends and a week or two a year, it will take a lot of years for a lead acid to succumb to cycle life, and an almost infinite number of years for a lithium to run out of cycles. In this scenario, lead acid likely makes more sense. On the other hand if you are using the camper for months straight and will for years, then cycle life begins to matter.
Lead acid has the advantage in cost and compatibility - you current chargers and isolators were designed to work with Lead Acid, so no changes were needed. If you have a vented battery compartment, buying commodity flooded lead acid batteries and using the snot out or them (80% DOD) then replacing them when they die or when the cost of lithium has dropped further may make the most sense. Unless you plan on using the camper a lot and keeping it for a long time, LiFePO4 will likely not work out from an economic perspective. However, campers in general don't make economic sense, so maybe that is not a real concern.
This is all coming from some one with a 150Ah LiFePO4 battery - in my particular case, I am weight limited and enjoy tinkering, so a low cost DIY LiFePO4 pack has worked out well for me.
