IMO, for your stated usage;
The best cam for this application is the stock one.
Any other cam, with no other changes, is pretty much a waste of money/time.
If it doesn't already have a 4bbl, but does have the typical 2.76 gears, and a stock stall, then installing a 4bbl is for your stated usage, a waste. The reason is that with say a 26.5"tire, 2000rpm in 2.45 low gear, is gonna be about 21 mph. Your 2bbl is not gonna roll off the power until maybe 3000 rpm, which would then be 30ish mph.This is about the time a 4bbl will begin, I said begin, to make power over the 2bbl.
Are you willing to wait?
By far the best bang for the buck for your your 318 Duster is a 2800 stall.
And next best is, 4-series gears; But, I don't suggest that lol. With a 2800TC, 3.23s would be adequate in your combo, and you can still hit the hiway.
The higher stall will allow the engine to spool up and find at least 20/25 horsepower over a sub-2000 stall. The 4bbl will not even begin to touch that at 2000 stall. nor will any streetable gears at zero mph. Nor will a cam until say 4500 rpm or more.
Only after the Convertor and gears are in, would I think about a 4bbl, and at no time, for your combo, would I consider a cam with a later closing intake. If you install a 4bbl, then more than likely you will need dual exhaust, but the iron log manifolds may still be a choke-point.
These are my opinions based on 50 years experience.
Lets say you put a 4bbl on it and it makes plus 15hp at 4400rpm which with 2.76 gears will be about 45mph. and it didn't START making power until 30/35 mph When you stuff it into Second at say 4600, the rpm will plummet to 2700, and that takes care of performance. tuck tail and slink off the track. Cuz at 2700, the 4bbl is not making any hp over the 2bbl, unless it's like maybe 2hp, lol.
Lets say you are a lil disappointed and install 3.91 gears. Now the 4bbl will START making power at 22mph, going to 38 mph. When you shift, the Rs will again fall to about 2700, and so now, yur done 7 mph sooner. :(
So now yur really ticked
And finally, you install a convertor, unlocking your 318 from it's drudgery of lack of footpounds, the engine spools up, finds a bunch of more footpounds and begins it's Rapid Transit to shift rpm.
Since I already told you this would happen, just do it first. Maybe you will be satisfied with what you get, and postpone the other mods. I mean, you said it was a cruiser; right?
Ok one more; Say you are idling down the road with those 26.5 tires and a 2000 stall, doing 35mph at 1200rpm, in top gear. Let's say you wanna impress the raging-hormones teenager in the POS tuner-car in the next lane, who is incessantly burping his throttle to keep his tiny dick hard. So then, as soon as you floor it, your engine spools up to around 2000, well not much power there yet, so the trans calls for a downshift, and hits oh say 2000 at 35mph, now in Second gear, Hmmm. So the trans goes to First gear and at WOT, the Rs jump to 3600, there ya go but, the tuner-creep is long gone.
Next, lets install a 2800 TC and 3.23s
Ok so, at 35mph, yur cruising at 1400 in Drive. On the downshift into First at WOT, the rpm jumps to 4200, oh chit, yur just about at shift rpm, but screaming at or near peak power, none the less; so you are kicking that tuner-boy, at least for a second, lol, as the engine races to shift rpm. But hey, the smile on your face is hard to ignore.
The 2bbl is still on it, as is/are the single exhaust and factory cam.
