My ex-boss had a look at the cam and lifters and gave me the "thumbs-up", which was quite a relief.
I dropped the "old" oil and filter, then gave the cam and lifters a bath in Lucas oil stabilizer (as a bit of insurance), before setting the intake back in place.
Before installing the valve covers, I flooded the rocker arms as well as the oil return holes in the cylinder heads with a quart of 10w30 per side.
After installing the valve covers and plug wires, I added a container of Comp's break-in lube plus 5 more quarts of 10w30 (it's an 8 qt oil pan)