If you dont have to bore the block and can use stock pistons it can b fairly cheap and run on 87 oct fuel.
some 4.0l heads do hot spot in the combustion chamber. Often polishing the head in the top of the combustion chamber around the valves can help. Get it nice and smooth, with out removing too much material. Piston quench height needs to be set correctly for it to run well. Thicker and thinner head gaskets are avialable. U can also shve the head or deck the block if necessary.