i will be dropping in a rebuilt 4 litre soon, does anything need to be changed to use a au metal head gasket? is it worth using one? also is it worth upgrading to ef, el style manifold and the like? how hard is it to do? and whats it roughly cost for all the gear? much gain to be had?
thanks

AU gasket, yes worth it, just bolt it in, you should never have a headgasket problem again.

EF/EL manifold will give you a little more power down low, but alot more torque, yes I think its worth it, having done it, you will need to also had a frequency switch from jaycar or similar to switch the runners.

Closed is long runner good down low, and open is short runner (roughly same as EA manifold) and goofd for up high.