J/X Head exhaust flow?

Back in 1985, I welded up a couple of J heads exhaust ports to raise the floor and make them look like my brother's W2 ports. Both heads cracked in the exhaust port across the valve seat where the crossover to the intake is so I got seats put in those two exhaust ports. I wondered if they would hold up so I never used them until around 1995 when I got the 1969 Dart and needed an engine to replace the 225 slant 6. My brother who worked at a tractor dealership and had access to valve grinding tools put 2.02 intakes in the heads and I ported them myself mostly a bowl blend and opened up the pinch at the pushrod a little. I also cut down that dog leg in the exhaust port roof some. They've worked good and made a little power but I don't know if it's much more than an unported set. The engine is a 340 with a .508 MP Performance hydraulic cam, LD 340 intake, 4.10 gears, A904 with low 1st gear and pinion snubber, it runs 86 to 88mph in the eighth dependent on the weather on street tires through the mufflers whatever that equates to in horsepower. I don't have any side by side comparison numbers though.