cam selection

I wouldn't recommend buying a used cam. It's just not a good idea. For $50-$100 more you can have the reassurance of knowing that your cam is brand new & should be trouble free. Just my opinion. And putting on the 1.7 rockers really isn't going to make much of a difference. If your pistons are notched...by all means keep your 1.7s instead of buying the 1.6s. You'll get a tad more power out of your combination. I doubt it will put any additional stress on your valvetrain and the lift that the 1.7s give you is still very streetable.