I have been faced with this problem for several years, my Volare unit is poised under the 55 dodge "hourglass frame" and ask myself why do things happen to me. I've seen all the Ford, Chevy and Dodge type B builds(48-53 plothouse) and even 60's era A100's all relatively straight frames and then my hourglass framed 55 Dodge comes along and if installed the frame rail collides with the Volare steering gear. Some law of physics states that two things can not occupy the same place at the same time. I've thought about cutting off the front of the frame as you did it but I would like the appearance of the stock frame as it exits the front sheet metal to attaching to the bumper to appear stock. I have even considered grafting rectangular tubes on each side, welding at front and back leaving the front frame and cross member and the removing rails where they get narrow.
The most elegant Volare graft I've seen is on the snapshot of a 56 Plymouth I have attached, The section of the frame is cut, boxed with three round tubes swoop out the the frame to hold the Volare in place then continuing on to support the bumper (done by a skilled race car frame builder).