Having not long ago replaced my heater core I commiserate.
Designers do not design automobiles. They squeeze things into a package presented to them by artiste types, subservient to the sales department, who keep crying sad for still more bells and whistles,
The auto industry should reads a little classic, "The Specialist".
This little book covers the correct and exact design of a proper out house, i.e. that which would be completely beyond the auto mob.
If you ever see a copy, grab it as it is no doubt of print.
P.S. Got me thinking, so asked Mr Google ---- "The Specialist" by Chic Sale" was the reply. I am checking further for the text, as this is THE handbook for all the so called experts.