the freeze plug kit i use is the dorman 567-014 can be had at autozone ...
it has 3 small press in plugs...
1 each part number 555-0008 which measures .580 inches
2 each part number 555-0009 which measure .590 inches
looks like one is .010 smaller...probably should not use that one...LOL
never seen at small block without them....i always install them...would not trust the cam thrust plate to seal the oil passages in front of engine...