having issues with temp going up to 210 on highway speeds... I could idle in park with A/C blasting and it stays at 185. Stop and go traffic runs at 190.... it's only when I go on the highway that it starts to over heat.....1966 Mustang with aluminum 3 core rad. one inch cores....sanden A/c compressor with 8 groove surpentine belts. 1:1 ratio on pulleys... want can I do to keep temp down at higher speeds...