Fuel tank sending unit

We received our VDO fuel tank sending unit and matched it up to our VDO gauge so we have the same ohms range. We've also had to fabricate a mounting flange to get it to sit correctly in our 78 chevette fuel tank, so all good there. I have two remaining questions which perhaps one of you can answer.

What length when you install the float is optimal to give the empty to full range. i.e. should the float hit the bottom of the tank? I think so? Any ideas appreciated, as the sending unit we have allows for the float to be adjusted.

Secondly, the sending unit we used doesn't have a fuel pick up tube to attach our external electric pump to. It looks like i might have to fabricate one of these as well, however I did notice that on the side of our chevette fuel tank I have a fuel filler tube (1.5" diamter") and a smaller one at 90 degrees in front of it....hmmmm

Cheers

The smaller tube is most likely the air vent for filling the tank. I don't have a Chevette  tank, but you need an air vent for sure. If it's not there, it will take a very long time to fill the tank.

Update. After many phone calls and searches we found a local tank and rad shop who could make an 88 fuel tank sending unit (90 ohm to match gauge) with feed, return and vent built in. Slight modification and adaption. Picked up tank today and it looks great and only cost is $150.00