You better use my made pressure/loadcapacity lists, they take better care of giving the same deflection of tire over the whole range of Pressure/loadcapacity.
First open the USA map with given in PSI and LBS.
then you can choose the submap for if you want it given per tire, axle single or axle dual, I would take the axle single , so you dont need to devide the axle loads by 2 anymore.
then first determine the reference-pressure(Pr)/Atpressure/maxloadpressure/pressure needed for the maximum load up to 160km/99m/h, wich is not the maximum pressure of tire.
If we are talking about your 70 psi in front tires, I think you have E-load tires with Pr/// of 80 psi or mayby D-load with exeption 70 psi Pr/// instead of the usual 65 psi.
Then download or leftclick the PDF beginning with the Pr.
In that list first search the Loadindex/maximum load in the first rows then in that line the load you want to know it for, and look above or below it for the needed pressure.
Always first add a 10% extra to the load before looking it up in the list.
The car-makers use nowadays the GAWR's to fill in for normal use , American pressure stickers only give that advice. But sometimes for heavy duty maximum load of tire is used or even maximum pressure of tire , wich gives terrible bumping when normally loaded.
The difference in gas- milage between this determined pressure and high pressure is not that big, but enaugh and not to high pressure gives better comfort and gripp, and less nervous stearing when on front.