I have my driver seat off of my 2019 VS30 to figure out alternator tap point, so I thought I'd add on to this thread for the record. My plan from prior reading was to use F150/4 no. 6, but I wanted to verify the actual fuse ratings. So I did open heart surgery under the seat to get the attached picture. The front of the van is at the top, rear at bottom.
View attachment 143195
Both 2 and 6 have fuses installed but unused. No. 2 has a 125A fuse, and no. 6 has an 80A fuse. Both of these match my fuse supplement. The 80A on no. 6 is perfect for my DC-DC converter tap point, I'm going with it. And better yet I don't need to install a breaker under the seat as I has planned, since it is already fused. I'll put a 60A breaker/disconnect in a more accessible place.