1990 Chevy Silverado Engine knocks when accelerating

5.7 engine Ran great no noise/issues. Radiator cracked, replaced, drove about 150 miles and water pump leaking/broke. Replaced continued on trip about 50 miles, returned home about 185 miles no issues. Started truck the next morning pulled out of driveway and headed downhill to first stop sign. When pulling away engine knocked sounded like rod to me at first. I have driven the truck about 50 miles since this happened. I can start the truck and no noise (runs a little rough, must keep foot on gas for a little while, this was not the case until this happened) I can race the engine while in park, no noise. After getting truck on fairly level road can get truck up to 40-50 with no noise assuming I do not need to press accelerator hard to get up to speed. In other words when up to required speed I can maintain that speed (assuming no uphill) with no noise.