318 head???

I do not think you can use mechanical pushrods with the hydraulic cam and the 273 mechanical rockers.

Absolutely they work. Being 55 I've done that years ago when I was to broke to pay attention. The rockers do not oil thru the push rods. They oil thru a hole in the head to the rocker shaft. The 318 and 273 PR on the lifter end are both ball ends. The difference is on the rocker end the 273 being a cup and the 318 is a ball.