So, if it was YOU welding this, what would you do?

[GWD]

I'd stick weld everything. 6011 on the first pass and 7018 for the cover passes.

Oh, and I'd use 3" x 6" thick wall tubular steel for the base (or whatever dimensions are necessary).

I did something like this for a car hauling trailer for use with a portable winch. The winch mount was put on AFTER this water tank monstrosity was hand winched on with a come-along. Ugh.



Here is how it looks on a metal bed. Underneath is a piece of tubular steel welded in for reinforcement.