Fun, Not Fun, Fuel hose Options

[NARP74]

For a 3.2 conversion that I was trying to bring out to a meetup on Sunday. Relocating my fuel pump to a better up front location, under the steering rack. Redoing some of the hose connections to make them longer. 8mm, 10mm for most of them from the tank and the supply and return lines in the car.
The Bosch fuel pump I have needs 12mm, maybe 13mm to get over the bulge.

I have;
5/16 hose which is 7.8mm, good enough for the 8mm connections.
3/8 which is 9.5mm, good enough for the 10mm connections.

I tried everything to get the 3/8 to stretch over the 12/13 mm needed to install on the feed side of the fuel pump. I tried heating in the sun on a black car, lazy way. Then I tried a heat gun. Then I tried needle nose pliers to stretch the hose opening out. Tried alcohol to slip it over. Nothing I did would get more than a 1/4 over the fuel pump inlet and then it would bunch up and not budge any further.

Then I went to the store and bought some 1/2 inch which is 12.7mm. Fits great over the Bosch fuel pump, but is too sloppy over the 10mm supply line from the tank. And I don't have a fuel hose clamp that big yet.

What's an idiot to do? I spent a day on this and am not much further along and I still need to wire it!

All of the hose is the good stuff from NAPA, Gates Barricade for fuel injection.

Help