a 318/360 performer has the larger 360 runner but necks down the last 1.5 inches at the head port

I have used a porting kit to open it up to a 360 size port gasket matching them

only had to go into the port the 1.5 inch or so

I think the LD4B I have does the same thing..not 100% sure though,but it is for the 318 heads

the street dominator is another small port low rise single plane intake that works well on a 318 head

I have never seen an sp2p that was good for anything other than to choke one down,great if you idle around town and never get over 3000rpms