I think I know the lifter sound you're talking about guys, it's more obvious when the engine is cold. Sort of like a tapping sound which goes away when the engine warms up.
But this is a rattle like no rattle you've ever heard before. You wouldn't suspect anything but the exhaust IMO. If the drivers door is open it seems to come from under the car at my side. I'll be sticking my head underneath and getting the missus to rev it up for me just to make sure. Haven't had a minute to scratch myself lately.
Not sure if the cam was replaced or what else when the engine was rebuilt, I was young and stupid back then (younger and stupider than now anyway).
I've been looking at new cars lately, so I should just trade it in and hope they don't notice it.
If it ain't broke don't fix it.