Does anyone know any of the flow rates for the #14/#17, and do they restict #8 heads in any way. I don't think anything was done to them and they are already on the car, and currently leaking. I am going to take them off to replace gaskets, just wondering if something else would be better? Personally, I dont like the oxygen sensor on the passenger side, and the block-off flap piece on the driver's side.

 

I don't know the flow rates of those but I know they aren't very good! Those #14/#17 manifolds are the 307's equivalent to the 350's #1/#5 manifolds of the 70's. The differences were the #1's had the rounded outlet for the exhaust pipe to bolt to and the #14 had the flat outlet which needed the heat riser valve for the exhaust to bolt to. The #5's were just like the #17's but without the O2 sensor.

If you're sticking to manifolds, consider swapping your #14 ( with the heat riser ) for a #1 without the heat riser. Keep the #17 and use the O2 sensor port for a wideband sensor to tune your car instead of swapping to a #5.