But, what makes you think resting pulse rate is correlated to aerobic fitness? My resting pulse was the lowest (46 bpm) when I was dieting, at my lowest weight, and just doing easy riding back in '03. Now that I'm eating and riding/training more miles, it's up to 52-54. But, my HR on the club rides is much lower now, so it's easier to hang with the group and not run out of steam near the end. That's what counts.
If you want a lower resting pulse, just cut 500-1000 calories from your diet, and restrict your exercise to a 30 minute walk a day. Bet you'll see a difference in a week.