I suppose if you want to reuse the iron heads it is to keep the original appearance? So you stay with a carburetor feed?
To choose the right configuration, I think you need to set a power and speed target. With a ratio of 3.77, I think the maximum power at 5500 rpm would be good, it would be around 85, 130, 180, 225 and 270 km / h on the various gear.
With my configuration, Georges thinks that I will have 490 hp at 6100 rpm but I will already be happy if there are only 450.
If that helps I can communicate to you by PM all the references, the suppliers and the prices of what I have chosen.