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I cannot guarantee, but most units of that vintage had a 4" drop axle, mounted above the spring pack.
Look at the existing axle and see if the spring perches were cut off and rewelded on the opposite side in order to flip the axle and get more ground clearance. If that was the case, you might be able to return it to the original condition by simply reversing the process.
In the original condition, the wheel hub will be in line with, or slightly below the bottom of the belly pan.