273 warm up!
Yes, the street 273 Commando was rated 235HP, not 275. You will not get the same performance just with bolt-on parts, because you won't have the CR. You can still get a worthwhile improvement.
That factory intake is a single plane and might not be the most effective for your build. They make a small port dual plane intake for 318s, I forget the name. Here's some info on Mopar cam upgrades.