What cam should I use on 318?

The Comp XE262 or Lunati 10200701 that Dano recommended are both good cams for your intended use. The Lunati is just slightly smaller but ground on a 108 lobe center so it'll idle about the same as the slightly larger XE262 cam but probably make some more torque to get you out of the hole quicker when spirited driving. I have also heard good reports on the Hughes whiplash cam RustyRatRod recommended. It'll idle more like a hot rod than the other 2 and still make good power without having to change the torque converter but it probably won't get great fuel mileage. If fuel mileage is much of a concern the Lunati is what I'd go with

The biggest thing about a flat tappet cam is to make sure and follow the break-in procedure to a T and always use oil with a good amount of ZDDP in it. Also make sure you use the recommended valve springs. If these things aren't followed it can lead to a destroyed cam (and possibly engine)