360 build recommendations

X J O heads are basically all the same. Within a couple of CFM of each other. Without doing some porting to get them to flow better they will be the bottleneck. Ede's would be a nice upgrade, clean up the bowls and runners and you can boost compression a touch to make up for heat loss from aluminum.

With ede heads and a good tune, you may get right at 400hp with a XE268H. you'll have to cam it up a bit to get 400hp with stock iron heads and drivability will suffer a bit.

Just my thoughts.