Re: 2 good cyl 2 bad... Lifters or timing?
Just read the other thread ... you are in for a rough rebuild.
If I were you, I'd pull the plugs and the valve cover and turn the engine over with a breaker bar on the drive shaft (don't use the starter - all kinds of bad things could happen if the camshaft broke). If there is action in the rocker arms for pistons 3 & 4, then you are lucky - it is probably just a valve stem that snapped and rebuilding the head will get you back on the road.
If you threw a rod, or if the rocker arms don't move, I'd call a salvage yard and cut your losses there. There is a good chance that the internal damage from throwing a rod or breaking the camshaft will make the engine unrepairable.