There are replacements for hi fi Sansui receiver (1976) ball socket AM antenna mounts as the original ones break easily. They are molded from plastic and of a simple design and have sold for over 15 years for $12. Making a mold for the Lionel / Kline GG1 side frames would be much more difficult to make but is the ultimate solution that will never happen.
I have just inspected my K-line GG1 bought when first issued in 2002. It developed a warped side frame after a few years and I was able to buy one from Lionel that fit perfectly at the time. K-line must have copied Lionel very well. The inspection showed two side frames straight and in good shape. The other two side frames show some minor warping, at least 1/32 inch or maybe more. These side frames anchor the needle bearings of the wheel axles and are critical to the operation of the lead and following trucks.
If or when my side frames warp enough or crumble and fail and none are available, I would attempt to make one or two. I would use 3/4 or 1 inch aluminum angle and cut to replace the side frame. An all plastic side frame probably would not be strong enough to hold the wheel bearing. I would rig up a hole or use the bearing part of the old side frame and JB weld to hold the wheel bearings in. Then I would find a piece of 1/8 inch plastic sheet and make a cover for the outside of the side frame. I would then use a Dremel Moto tool and small cutting bits to attempt to carve out some plastic to look similar to the original side frame and paint it semi gloss black.
From a small distance the new side frames will not be noticed by most especially if two new ones were on one side. I am an operator and would accept this type of fix and know many other would not. But at least I would be able to still run my GG1.
Charlie
