depending on what compression, even stock, the cam makes all the difference
you should be able to do it

 

i see no prob hittin 300 with a 318 but are you really wanting to spend the money on building a 318 up im still wanting a 340 myself and what i have done seeing how a 318 340 360 are pretty much the same got a good running 318 changed the intake carb dist did a mild port job on the heads besides the heads all the other goodies will go on my 340 when i find the right one if the 318 runs good the way it is why not just keep it that way and save for your motor then build the motor up on a stand
goodluck

 

are you building it for the street or strip?

 

hey tyler
as for cams i wouldnt get too crazy with it as it is a 318 id goe with a stock 340 cam as this is what i think is in mine not sure though got the motor that way im running 2 1/4 pipes all the way out the back with mufflers from discount auto cant exactly remember the name of them end with a flow something flow going there this weekend and i'll check for ya i saw a article in mopar muscle about them saying it was the closest sound for factory muscle car sound plus it doesnt sound like all the mustangs and chevys running flowmasters i think they all sound the same i had another set of mufflers on my 68 cuda formula S 340 car that were thrush turbos that sounded really mean but i also was running a 312 mechanical cam i had those coming out just before the rear tires im saving my money up and im getting some flow tech headers for the dart this winter as im having problems sealing my 340 exhaust manifold up to the small exhaust ports on the 318 as for a carb im running a manual choke edelbock thunder series 650 cfm with a mopar performance M1 intake and a direct connection electronic dist M.P chrome box my orange one crapped out on me ,M.P high voltage coil and a 1/4 ohm ballast box all this stuff will be going onto my built 340 or 360 whenever i find one and get it built im also wanting to get the mopar aluminum heads or atleast a set of edelbrocks but trying to keep it all mopar with all this being said the dart sounds pretty mean and goes pretty good kinda bogish on take off with the M1 though on take off still fine tuning the timing but in the rpm range for the intake it really pulls
goodluck
Terry

 

what sort of sec: bracket are you looking for out of a 318 , ill tell you what you need but it will cost a few , ill give you the break down for that bracket if you would like .... when i say it will cost you its just for the parts you will need not for me hehehehehe anyway let me know and ill try and help ok

 

If it was me, I wouldn't spend a dime on the 318, only to keep it running properly and spend the money on the 340 or 360.

If you really want to spend the money on the 318 then I'd go with a carb, intake, headers, dizzy, coil, wires, and cam (if you want to tear into the motor) that will also work with a 340 or 360, depending on which one you get. Cams can be tricky with their specs so I'd wait on the cam til you get the larger motor. Since you'll be swapping the parts over, get good quality parts.