In changing the heads, Do I need to also remove the cylinders and replace the base gaskets?

 

It Depends. Do you want to? Why are you replacing the heads? Just a performance upgrade? If you're careful, you can just R&R the head without disturbing the base gasket, but there is still a risk that it will leak afterwards. "The right way" is to put new rings in and hone the cylinders if you take them off.

 

Dr Hess,
I have an issue with the rear cylinder, a rear mounting bolt boss area for the rocker broke, we tried jb welding it but still have an issue with oil leak between head and rocker. I wanted to just replace the rear head.

 

.Go back with Cometic gaskets.

 

If your going to through the steps to removing the heads you might as well pull the cylinders and deglaze the cylinders ( at very least ) and replace the base and head gaskets.