What cam should I use on 318?

Lunati VooDoo 10200701
Performer, Action Plus, or stock 340/360 4bbl intake
500 or 600 cfm carb
Good Manifolds or TTI/Dougs headers

Degree cam, use recommended valve springs, use a new quality chain and the Magnum chain tensioner.

Not to hijack, I am looking for clarification on a subject.

I have pretty much everything you're recommending here on my 318 except the headers (which are on the list) and the timing chain tensioner.

I've been searching and I am not seeing WHY one needs to suddenly put a tensioner, on an engine that's been running fine for the last 48 years without one. What does my engine benefit for the $45 +/- that the tensioner gives. That $45 can go to some other parts, like break in oil for said cam...

I found a link to what it does here, but not the WHY it's needed on a 318.
http://repairpal.com/timing-chain-tensioner