Bottom End Rebuild Planning
Note that on a slant six, the distributor gear and oil pumps drive gears are separate gears running off the same cam gear. There is no reason to upgrade the distributor gear, and while the oil pump gear could use help, there's no off the shelf option there. Some builders rig an oil squirter to lube the gear.
Roll-Master / JP has the only timing chain still in production worth considering for a performance build. Everything else uses that thin three spoke cast sprocket that is known for breaking at high RPM.
You'll need to machine the valve guides to clear high lift cams. And definitely port the head enough to clear up the rough transitions.