You want the lug to be about as tight as you can get with a simple tire iron and the threads lubricated.
That is going to be right around 65-70 and after you drive the car around 50 miles or so, go though at least one heat/cool down cycle, recheck them.
What they mean by 48 is that you tighten the lugs in a criss cross pattern starting at 48 and increase in about 5 pound increments until you get them tight.
60 ft-lbs is not enough. Trust me. You are going to loose a wheel at that. Ask me how I know? Welding up 10" Campis because they came loose, fell off and cracked as a result is not what you want to worry about.
70 really isn't too much either. Put anti-sieze compound on the threads as well.
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