I think those heads were over the counter replacement heads. Are they ok, yes they are. The heads are big for what you want to do. I ran the early Merlin heads which were copies of those heads with raised exhaust ports. The issue is what do you want to use the car for. If it is around town driving, then a smaller port would increase low end torque. The larger port is better for higher rpm, such as racing. Those heads are about 320cc intake ports and can handle up to about 725-750 hp. I ran Dart 325cc heads on my 509 and they were a little small on my 540. If you are around town driving and staying below 6500 rpm max, I think a good 781 casting head would do great. But if you plan on shifting it at 7000 plus than the 990 head is pretty good. The only reason that people say they are not worth using is that machine work is expensive and by the time you sink the money in 990 heads, you could buy aftermarket. Also the issue with pump gas and steel heads, 10.5-1 is about as high as anyone wants to risk running. Some won't even go past 10-1.
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