From that vintage and model 283, it should have come stock with a solid lifter cam. Try starting with the factory settings. If I recall correctly they used to call it a Duntov cam or a 30-30 cam and the .030-.030 was the valve lash. I have not known too many small blocks that called for less than .022. If you are not able to find a actual specs, you could start adjusting both the intake and exhaust at .030, then work your way tighter .002 at a time until you get down to .024. See where it runs the best. I would adjust the intakes first then the exhaust. Often times the exhaust spec will be .002 or .004 looser than the intakes. This is to allow for greater heat expansion of the metal on the exhaust side. In most cases adjust them with the motor warmed up.

Pat