The original 340HP cam would work well, I believe. An Edelbrock dual plane with a 600cfm carb, as mentioned, should be just right. Especially with a set of headers and a good under-car exhaust system (2.25" pipes, typically).
The smaller valves in the 318 heads can "tame" that 340HP cam a bit, but not too much, for a good-driving/acting engine. A key thing would be to get the exact repro cam, not a "re-interpretation" of it by some cam company.
When "done and tuned", you might be surprised at how well that little vintage 318 might be!
After you do the engine, you might then plan on getting the trans overhauled with a few, select upgraded frictions in it, for good measure. Especially if it's a 904. "Hot Rod" did an article, back in about '68, on upgrading the 904 to better tolerate drag racing. Mentioning that the 727 would take more power to run, but with a few upgrades the 904 would do just fine and not absorb quite so much horsepower. At the time, they used B&M Transmission items.
Enjoy!
CBODY67