When sourcing Chevrolet 350 cylinder heads, you must prioritize material composition (Cast Iron vs. Aluminum). Aluminum heads offer superior heat dissipation and weight reduction, while cast iron provides durability for heavy-duty applications. Key specs include intake runner volume (typically 170cc to 210cc), combustion chamber size (64cc or 76cc) to determine compression ratios, and valve sizes (commonly 1.94/1.50 or 2.02/1.60). Ensure the bolt pattern is compatible with the specific block generation (SBC Gen I vs. later versions).