Remember and keep into perspective two things here, those readings are PARTS PER MILLION. They are way short of anything catastrophic, so you are just in a cautionary area waiting for another lest. Ignore anyone at this stage that advises a teardown. Overall, you can't tell much from two or three samples anyway. In order to make logical sense of wear trends that are not immediately catastrophic in scope is over many tests... 10 + over years of operation. If you were seeing 100 ppm versus 33, you would be allowed to run in circles and scream incoherently based on one test. ( : < )
That is not necessarily terminally high lead, but it ain't good. I don't see much else. Bad bearings are usually lead AND tin AND copper. Your copper and tin are low. A good sign.
Was this last test with the Lucas? If so, it didn't seem to thicken the oil out of grade, but the test prior was thickened out of grade (for whatever reason). The last test was 20.3 cSt at 100C (212F, the usual temp for the viscosity grade rating) and that is at the top end of 50 grade territory, nearly into 60 grade... and that's too thick!
Sudden high lead can sometimes be a large chunk of something that got into a bearing and did some serious scraping. In that case, it's a one-time thing (usually) that the engine can survive. I list this possibility first because you recently had the engine apart and an engine component failure, both of which can put large and small contaminants in the oil... and stuff like this can happen down the road as bits or pieces are washed out of the nooks and crannies. If you get unlucky, a big chunks is past the filter or goes past the filter when it's in bypass (during a cold start for example). Overly thick oil makes the likelihood of filter bypass even greater. The filter bypasses because the oil is too thick for all of it to pass thru the filter, so some of the dirty oil bypasses the filter. In essence, the thick oil could've left a big chunk of something bypass to the bearing and created the high lead situation.
Lead can also come from oil or fuel additives (or fuel).
What filter are you using? If it's not the FL1995 (PSD) or an equivalent, there is another positive step if you are worried about contaminates. The FL784 is a low efficiency filter. The FL1995 is a high efficiency filter.
The oil pressure test will be a good test of overall bearing condition. That should be your next test. Factory specs (from the factory manual) on thoroughly warmed up oil are: Idle= 10psi or higher, 2200 rpm= 40-70 psi.
I strongly advise NOT using the Lucas. As was said above, it can increase viscosity across all temperature ranges, increasing the likelihood of oil filter bypass on cold starts and contamination. The increase in viscosity could distort your oil pressure readings, too. You want readings from warmed up, 15W40 grade oil so they can be properly interpreted. As I said, at 15.2 cSt on the 100C viscosity test, the oil is within grade right now, with or without the Lucas, but if you do ever run more oil pressure tests, avoid additives that will thicken the oil and throw off the readings (thicker oil = higher oil readings... to interpret them correctly, you want to get readings on warm, unadulterated 15W40 oil).
DELO is a great oil! Unless you were using some unrated, low-rent peewater oil, a change of brand is not likely to help with this problem.
PS- You had coolant in the oil previously and in high amounts, it can be very ******* bearings. What was the cause of the previous high coolant?
. I remember dumping some of that stuff in my 62 ranchero 289 engine. It was cold outside and that stuff was thicker than molasses. Not so sure Lucas is good for cold weather operation though. 
