You could make a little threaded jack to fit inside the tower and lightly press/support both pins (pushing them outward) while peening/riveting the outside ends. Backing up the opposite side with a heavy hammer while riveting the other side with a lighter hammer would also remove some stress from the cast iron tower.
Same could be down with a bar/block of steel fit in between both pins if it were just the right thickness, or few pieces stacked to right thickness.
Or with cover removed rivet one pin at a time using the horn of an anvil or something similar to support the pin from inside.
