Ropak Corp., Fullerton, posted net income of $1.6 million for 1987, a 6% gain over last year's $1.5 million, while revenues hit a record $69 million, 45% higher than the previous year's $47.6 million. In the fourth quarter, net income totaled $378,000, contrasted with a loss of $74,000 in the final quarter of 1986. Revenues rose to $17.9 million, a 48% increase from $12.1 million a year earlier. Results for 1986 were restated to reflect an accounting change, which increased reported net income by $489,000, and by $44,000 in 1987. Ropak is a maker of plastic packaging and materials-handling products.