nothing wrong with using a fluxcore welder, you just do 10x more grinding than the mig guys do
don't know if you've read thru my build, but i used a lincoln weldpac 100 fluxcore welder
on all of the frame and most of the body modifications on my 58 truk
it's definitely the hard way to do it, but it keeps cost down and you'll never run out of gas
i do think your jumping around, working on unimportant stuff like front fenders
when you have a firewall, floor and pillars to fit and weld in
that said, i built/customized my bed first
you do have a 58-9 radiator support and inner fenders, not sure they'll play nice with 57 fenders
firewall is 58-9 just keep that in mind when you mount the hood hinges, holes are different