And each requires different rear axle hitches.
The early A-frame style on the left uses rear axle brackets that mount ahead of the axle housing.
The later A-frame style on the right uses rear axle brackets that mount under the axle housing.
Your two frames are for different models of tractor.
The “A” style is for short frame mid-to-late 60’s tractors. The one with the parallel frame members at the end is for long frame tractors from the 70’s onward.