I bought a new tank because I thought mine was leaking from being pretty rusty. Turns out it was just leaking from the front rollover/vent valve. So installing a new tank is not going to happen if you do not fold down the seams along the sides first.
Right now I have the new one in but cannot get the straps on.
While I had the sending unit out I figured I would look into the bouncing gauge problem. It's a simple slide resistor and I believe it is the poor connection it makes that causes the gauge to jump. Even with a meter connected to it and not touching it would show a fluctuating resistance that would eventually stop and hold steady. In other words unless the style or quality of sending unit is changed the gauge will never read better. It might be possible that adding a capacitor would slow the gauge movement to prevent false readings from sloshing.
I wanted to clean the slide resistor with some electronics cleaner but I was out. Maybe the fuel causes a varnish buildup that also causes bad readings.

 

So your saying that the new fuel tank did not have the edges folded along the sides? Bet those edges are pretty sharp!

Yes on the fuel varnish on the resistor wire. A very light sanding works too. As far as adding a capacitor to dampen the resistance changes; I thought that the instrument panel had a cap for this already....but I have never actually looked...just would think it would.

Also check electrical connections at the fuel pump and the ground connection.

 

Well it's good to hear I was thinking correctly on the varnish but how can I have older vehicles with no problems at all? It seems S10 specific which I find strange.
As far as the tank, I understand some tanks on other vehicles may not need them folded to be installed, so I wouldn't expect them to be pre-bent.
I just wish I had paid attention before making all the hose connections first. Now I get to decide between 2 hours fighting the last strap or 2 hours to drop the tank and reinstall after bending the flanges.

 

I just got longer bolts for the straps and cranked it on

 

Your 95 Blazer already has a buffer for the fuel gauge. It's either in the cluster, or a module in the dash, can't remember 98 and newer, the buffer is built into the fuel level sender in the tank.

 

I had to replace the bolt section on the small part of the strap. It's 4wd and they don't sell the small part of the front strap. So on my second attempt last night I got it to the point where a longer bolt would work. So I found a longer bolt and with a little TIG time it should go together tonight.