[SCOTI]

Steep learning curve but you're getting the hang of it.

On the wire size…. The smaller dia wire works better on thinner stuff (think sheet-metal or slightly thicker). The thicker diameter is used on stuff like frame brackets or sheet stuff over 1/8". Of course, w/each change you'll have to re-adjust settings according to your material. I always keep a spool of each handy. The later pics have your tack welds looking much better. I like to do a series of tack welds, check the fit of everything & if good, grind the tack welds down @ that time. Repeat after each round of tack welds & you get a more consistent weld seam vs missed areas between tacks.

On your Blazer tank, nice job w/the in-tank pump mods. Been looking @ that same kit for my Blazer tank as well (I've been eyeing the TB style aftermarket FI set-ups for the SBC in my 64 build). I would recommend supporting the bottom of the tank as the flange alone was not intended to carry the full weight & will probably cause issues on down the road. A strap set-up can easily be made to work w/your mounting arrangement since you can fab & are getting better w/the welder.