Yeah, you have officially screwed up the engine with the Lucas crap. But it sounds fixable. Lucas is nothing more than polymers that thicken the oil. The polymers will condense out of the oil on the parts causing the sludge. If the fix is going to work, this is what you'll need to do. Go to Walmart and buy an oil filter and a 5 qt bottle of Super Tech oil in 5w-20. Buy a qt bottle/can of Marvel Mystery oil. MMO is a solvent and will clean the oil screen fairly quick. Run that for 1000 miles in the next few weeks- NO short drive cycles. Change the oil again using the same oil and a bottle of Auto-Rx. Auto-Rx is a lanolin ester based product and will slowly clean the internals doing no damage. Run that 1000 miles, change the filter only topping off the oil. Run that 1000 miles again and change the filter only topping off the oil. Change the oil and filter. This time use Rotella 10w-30 motor oil. You might have to run the Auto-Rx thru the engine several times to get it cleaned up.Once cleaned up, go back to any brand 5w-20 oil wearing the Ford spec on the back of the bottle.
If the drain holes in the heads are plugged up, this probably won't work and the engine will have to come apart. You might try the following. After running the engine and it's at full temp, open the oil fill on the valve cover, bring the engine up to 2000 rpms and hold it. Watch for oil to come up the oil fill. If it does, the drain holes are plugged and none of the above is going to do you any good. The engine will require a mechanic to manually clean the top end of the engine. If the drain holes are plugged, the engine has basically pumped all of the oil out of the pan onto the heads where it fills the valve covers and the oil pump starts pumping foam- not a good thing to happen.
This is where I would start with your problem.