Strength is without a doubt a great advantage in rugby. The stronger you are, the more useful you'll be in rucking, mauling, tackling, scrums, and lifting in the line outs.
However, the main thing you should be working on is your endurance and speed. 70 minutes of running is no joke, and it takes a great deal of stamina. It doesn't matter how strong you are if you can't catch the guy with the ball.
I'd suggest you do a lot of HIIT, simply because it closely mimics the type of running you'll be doing in game situations. During the match, you will go through a continuous cycle of jogging, sprinting, and hitting--but never walking.
So to answer your original question, continue lifting, but supplement it with as much cardio as you can handle. Also, emphasize lifts such as cleans, squats and deadlifts.
Hope that helps.
(This is all assuming that you will be a forward, and not a back.)