GP-9 fuel tanks

A few days back (20 November 2019, to be exact), "Star Metro," the free giveaway newspaper in Edmonton, had a large front-page photo of two (heavily re-built, chopped nose) CN GP-9 locomotives (illustrating, or at least advertising, a new story about the current CN strike).
There are obstacles blocking the view of the edges of the fuel tank on the unit (7062) closer to the camera, but the further unit (7020) has -- not the curved-side fuel tanks one associates with EMD units from more than a decade ago, but -- a fuel tank with a side profile reminiscent of that on a GE U-boat: two planes meeting at an angle, vertical side for maybe the top 40%, then angling in toward the centre of the locomotive.
I assume that this (simpler) design of fuel tank was fabricated in CN's shops and applied to the locomotive in some rebuilding.

Hmmm.... I don't seem to have been looking carefully at CN Geeps lately. The angular fuel tank seems to be standard on many rebuilt GP-9, and has been for a while. Looking (at "Fallen Flags") at CN GP-9 in unrebuilt condition, it looks as iff many of CN's GP-9 units were originally built with very small fuel tanks. (Probably for the same reasons that made CN buy significant numbers of light road switchers, such as the GMD-1 and similar Alco (well, MLW) and F-M (well, CLC) designs.)
So many may have been rebuilt with larger-than-original fuel tanks, fabricated in-house.

I’ll go along with the last post. To make an EMD style tank would require the sheet steel to be rolled into the curved shape. The GE style just requires the plates to be welded up. Maybe the side sheets are bent into the 45 degree angle. It probably has to do with the cost of fabrication of the replacement.