318 Build on a small budget

Hey there,
I need a motor for my 67 Dart and it came with 3 318s, 2 were junk but the last one is a police interceptor 318 from a diplomat (not sure on the year) so the setup would be that 318 with a 727. Im looking for suggestions on how to get a little more power cheaply. I have a 4 bbl intake for it and headers and a Holly 600cfm 4 bbl. otherwise its a stock police interceptor 318. The only other think I was thinking was a Cam but i have no idea what size?

Any help on the Cam size and any other suggestions would be great!

Thanks