which intake for my engine

Most factory iron 4bbl intakes were large port for the 340/360 heads. On a 318 this creates a slight "step" in the port. On a mild combo like yours, this probably wouldn't be much of an issue.

The only small port factory iron 4 bbl intakes were the 273 intakes. These were a single plane, low rise intake. A Performer would be a definite upgrade over one of these boat anchors.

Good used Performers can typically be had for about $100.