I reiterate,not here to argue.
I would not open the intake side,for velocity in port.235 cfm will support up to 500 plus horse power,Im thinking 260 plus horse power.That is why I would not port the intake side .If there was a problem on the intake side I would fix it,nothing else. 2.02 valves fit on a 283. 461s can be finished at or close to 64CCs .porting exhaust side is self explanatory. 112 lda? please explain how that would work on a 6500 RPM 283?
If I was building a 420 horse power 283,I would use heads that flow 240 cfm and still use an intake center line at 102-105.If I use a carb bigger than a 4777 ( 650 double pumper)I would use a 4777 with a base plate off a 4781 (850 double pumper base plate) If you look at my ideas you will see that I mostly recommend items that are high velocity (moderate/small ports,carb with small venturi,moderate lift cam, 2.02 valve with small ports and lower lift) the flow numbers are plenty to support 300 HP. If you have a 283 engine that make 250 plus horse power at 6500 rpm,you also get extremely responsive throttle and the lower ICL makes for the punchie power band that makes a small engine fun to drive. The idle would be a little lumpy but not obnoxious like some of the silly 300 duration hydraulic flat tappet cams.
I admit that no engine combo is perfect,but if I can borrow from the master,Mr Tech,combination combination