There was probably a lot of residual moisture in the crankcase and block from the first failure. You're likely seeing that condensing on the cap. Like I said, crack the oil filter or drain it all into a clean bucket. If it looks like chocolate milk, you're in trouble. If it looks clean, put it back in and run it. Might not be a bad idea to shorten the interval for the first oil change after the head gasket replacement. Extended full temperature engine runs are the best thing to help burn that off. Short trips typically compound it.
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1979 CJ7, FI 5.0L Ford, NP435, D300, Full floated D44 Detroit, D30 Detroit EZ Locker.