The stock 318 hydraulic cam was 181/192 duration at 50, 0.371/0.399 lift. That cam is at the top of the range for a stock 318. Yes, it appears to be the 340 cam. Your stock mid '80s 318 is very easy to overcame as compression is low.

I am assuming you want to drive your truck. My suggestion would be the Comp Cams High Energy 252H. 206/206, .425/.425, 110 LSA. I think it'll have more snap than the 340 cam in your 318. You can use stock springs although you can change them if you wish. Break in the cam with the stock springs. Find the 340 springs on Rockauto, Enginetech ERV901, $2.00 each

The only thing that has to change is if you have valve rotators on the exhaust valves, they have to go, along with the short springs. Replace with regular retainers and springs.

Good Luck!

R.