I think that the reason for Winchester not making a toggle link action in .45-70 was probably more due to the length of the action that would have been required, rather than the strength of the design. The model 76 was built in .45-75 and .50-95 calibers which would probably have just as high pressures as the original .45-70. The model 76 is a very heavy gun as it is, so lengthening the action to handle cartridges of the .45-70 class just wasn't practical, in addition to the model 86 and later Browning designs being much stronger and suitable for the smokeless pressures that came later.
