If you think a simple cam change is gonna make the motor quite a lot faster, you have another think coming.

In my opinion, you'd be much better off saving up your money until you can afford some AFR 190 heads instead of wasting money on a cam change and trying to crutch-up stock heads.

I am very conservative when I'm suggesting parts for YOUR motor and spending YOUR money, but the cam I suggested is the one I would choose for my motor in the same set of circumstances. Any more cam than that and the motor will be sluggish with the tall gear and stock converter.