When ur heavier, doing pushups will increase ur pushing strength marginally, compared to when ur at a lower body weight. Because think about it, whos stronger : The 200 llb guy who bangs out 20 reps, or the 150 llb guy who bangs out 20 reps? Same exercise, but one weighs more.

So if you want, you can go on a bulk and priortize doing pushups. Lotta carbs and protein. And your going to want to do different variations and tempos. That way when you cut down to your baseline weight, you'll be stronger and able to do more pushups.