[blucar]

I would make a guess that if the rear end under your car came from a pickup, the spring is a heavy duty unit, in lieu of being a passenger car spring.
I also wonder ?, is the Columbia you have a correct 35-36 unit or has it been built up from later model parts?
My '36 had a Columbia when I bought the car in '52. Did not like the early units so I replaced it with a '42-48, which is actually a '48 with the stock sway bar attachments. I used the '36 banjo/drive-line with the '48 spring. Everything bolted together with no problems. The ride height is perfect, matching up quite well with the 2" dropped front axle.