Try 380 or 390 series aluminum alloy. 17-19% silicon for 390..., 7.5-9.5% for standard 380 alloy material.

Hypereutectic 390 refers to a unique aluminum piston alloy that contains dissolved and free silicon. The material can be T6 heat treated to high strength and stiffness. Non-heat treated 390 hypereutectic alloy aluminum has slightly less strength than conventionally cast F-132 aluminum. You can machine it and use it...

Remember the K&B .65 Sportster engines that used no crank shaft bushings or cylinder liners...Smiles