thanks, Can a stock rear end be built up for moderate driving meaning stepping on it a occasionally
Yes. However, the expense of a posi unit, ring gear, bearings, seals, gaskets and other parts including axles will cost much the same be it a Chevy, (stock or 12 bolt), 9" Ford or a Dana 60.
With any of the others mentioned, there will be the need to have spring pads installed and some issues with brake cables and items will require some engineering/time and expense.
The term "Stepping on it" can be the issue and problem regardless f the type or strength of the unit. How it hooks up and applies the HP. Temperment. Sucsessive times.
Many stock unit was, is and will survive under extreem use.