I am looking at the Porsche 914 Factory Manual Volume 1 (914-4 Engine & Clutch) On page 6.3-2/2 There is a chart on reconditioning of crankshaft which gives the crank pin diameters for the mains and the conrods. The first on the list is a new or normal main bearing pin which has a rated diameter of 60 mm, then it shows a measurement called lapping diameter one being 59.990 mm the other 59.971 mm.
I would like to know what the lapping diameter is, what is meant by "lapping dia." ?

lapping = polish

licking if you are a dog....

Polished dimension, agreed.

Thanks for the responses, Can I assume then that as long as the polished dimension is between 59.971 mm and 59.990 mm I would be good to go with standard main bearings?

Yes

Thanks