will 360 j heads fit on my 273

68 Sedan has a good point. The bigger ports will have less velocity. As Rick Mudge once told me "velocity is torque". Rick ported heads and flow tested them for a living. Higher velocity also means more manifold vacuum. The port diameter needs to be increased with engine volume to get the same velocity, which means bigger engines need slightly larger ports than the smaller ones to have the same velocity.

The J heads have 70 cc chambers. If your 273 is a 67 from your Barracuda the stock heads are 57 cc's. If you bolt them on to a stock 10.5 4-bbl engine your compression will drop to 8.79, and for a stock 9.0 2-bbl engine it will drop to 7.57. You would need a 11.0 compression piston to give you close to 9.0 final compression with J heads to run on pump gas.

If you are going to use the 292 duration cam, you should put around 12.5:1 pistons in and use a single plane manifold with the J heads. It would not be a "daily driver".

If you want something "streetable", I agree to stay under 280 duration, use the 273 head with some mild clean up porting - 1.88 intakes and 1.6 exhaust with hardened seats, and dual plane (performer is ok, I used a Wiand Stealth on a 360 in a 78 Warlock 4x4 stepside and was happy with it - It has a power band from idle - 5500 RPM). The Stealth has nice low end and still keeps high RPM power. The best dual plane for the 318 273 heads is the Edelbrock LD4B. It is the LD340 manifold made for the smaller ports. We just put one on my son's 318 Valiant with a stock cam and a new Edelbrock 625 carb and it has great low end pull on a stock 318 with a 4 bbl and dual exhaust - no bog off the line and good throttle response.