i got a 78LTD2 with a 514 in it. i used a set of hedman headers and 2-1/2 exhaust with flowmasters. sounds good and runs good although i'm considering removing the flowmasters and using some magnaflows. its been found that the flowmasters might be a bottle neck as rpms increase. on 460.com there has been several people who gained more torque and horsepower with just a muffler swap. good luck with your Ranchero there are not many good looking big block examples out there.