64 barracuda 273 engine timing

It's as much advance as it will take without pinging or 10 before....whichever is higher. With today gasoline, I'd be surprised if you can advance it to more than 5 BTDC. If it pings at TDC, you need better fuel, water injection, or you'll have to build the engine with lower compression. Trying to run an engine with ATDC timing will usually cause it to overheat and get terrible mileage.