Do you have a 1958 Truck Shop manual, and 1958 Truck Owner's Manual?
https://www.classicparts.com/1958-Shop-Manual-Chevrolet/productinfo/04-016/https://www.classicparts.com/Owners-Manual-Chevrolet/productinfo/04-128/Have you checked/set the points?
Do you have a vacuum gauge - to let you do a quick-and-dirty (and close to correct) adjustment of timing and carburetor?
Is you engine a car engine or a truck engine?
Have you set the valve lash/gap?
What is the code stamped into the block, in the ledge to the rear of the distributor?
