I may add, margin of error for flow testing should be taken into account. I flowed 2 ports on each head and took the average. Most stock 318 heads crap out and most performance cams are less than .480 lift anyway.
For future reference and kids that find this later.
It's not worth buying the tools or taking heads off just to port or port match One set, it's only worth it if you already have the tools and shop setup to port and are building a 318 to make more than 300HP.
Agreed. Yes there is a port match problem but a stock 318 it doesn't matter. Use the 340 gasket as stated above.
Did the swap way back in 1975 when I spun a rod bearing on my 340 Duster .No money to fix the 340 but a year old 8,000 mile 318 only cost a $100 junk yard price back then.Ran fine for 10 years till rust turned the Duster into dust.