Lik; the rockers and rocker shaft look to be in very good condition. A lifter should fit in the area [space] just below and between the pushrod holes. But there might be excessive casting flash. And not all of the spaces will be big enough. Check the ball end of the pushrods, they should be shiny. The exhaust manifold gasket would cause a ticking sound.
Put it together, fire it up at an idle, and check it with a stethoscope. You'll find it.
