Though I have an IFS under my '31, I have a wood block made up that goes to the underside of the front cross member. Then, when I put the jacks under it, I then put them under the frame. There is no reason you can't jack using the axle though - that is if you have a low enough jack. Ford used that basic 'I' beam axle from inception through '48 and you just have to believe that most folks used it for a jacking point if they wanted the entire front end off the ground.
This is where I place the stationarys;
