If your 318 is factory (1984) your pistons should be pn 3698571 with no valve reliefs (flat) and a 1.74" Compression height. considering an aftermarket performance piston is 1.81" compression height that's close to "zero deck" you get the picture.
FWIW I have an 80's 318 like yours that has been "re-ringed" and uses the 1.74" compression height pistons along with 2843675 casting 318 heads which have 1.78/1.50 valves and 69cc chambers. Turning a Delta Cams 211/218 cam 425/435 lift on 112lsa with a cast spreadbore intake and a 800 cfm Quadrajet calibrated for 4700'.
The engine pulls my 1/2 ton Power Wagon down the interstate at 85+ with no more than 1/3 throttle. It doesn't blaze the tire, but its got plenty of power to pull that pig around. We use it at 7000' and it wheels fine. No reason to hate on a 318.
Good luck with your project.