Most small block chevys can be modified to have 4 bolt mains. It is a fairly simple machining process. There are high performance applications where smaller displacements are needed either to conform to rules or to meet class requirements of weight to cubic inches. I don't know if they still are, but various configurations of 283s and 265s were popular in NHRA Gas and modified classes where you might have a 3500 pound car with a 283 to fit into F/MP or E/Gas. Since these motors were small, they made power with RPM and gear multiplication. Many of these cars had 6.17-1 gears in the rear end and were turning over 10,000 RPM going through the lights. Other places you might find these small high reving motors is at Bonneville or Indy style racing. So while a 4 bolt main 283 may not have been made by Chevy, we all know that hot rodders will do whatever it takes to go fast. You have a piece of hot rod history there, hope you are able to put it to good use.

Pat