Aircooled VW South Africa

I have found that most shops overlook a lot of basics when it comes to beetle engines even supposed experts are sometimes lax when it comes to the bug.
Should you have to rebuild the engine here is some of the things I look for when building a standard engine.
Select the casing carefully I have found it best not to linebore more than 2mm for long life les is obviously better. Check that the center main saddles are not distorted torque an empty casing and shine a strong light from one side if you see daylight at the parting line the casing is best left alone I know that the halves can be skimmed and re used but try line boring one of those it seems that the metalurgy changes with heat and it is extremely difficult to get a good cut. the distortion is more common on AS 41 cases.
Check all the studs for stripped threads
obviously the cylinder head studs but those around the cam (both sides at the plug) is also prone to damage.
whenever you line bore have the cam tunnel re traced normally very little is removed and only from the center bearing. I dont like painted blocks and if you have one of those with a little number plate attached next to the fuel pump....... beware!
If the casing has been skimmed beware that there will be shims under cylinders and an od sized bras timing gear (big hassles if it does not get re used. The last main area when line boring is the cutting of the thrust surface at the rear main bearing Std 22 mm 1 and 2 mm oversizes are available with 2 mm usually supplied I normally just clean upm the wear and modify the bearing to suit. the other real problem area is cracks normally behind no 3 cylinder but also at the oil cooler mounts

Casing continued
The rear of the casing is also bored sometimes for a larger crank pulley the std size is 50mm and is usually bored to 50.5 mm for which an over size pulley is required. I have also found some casings with only the rear or center main bored so check all if you feel a line bore is not needed.
the oil channel at the smal main bearing is also prone to clogging and i usually drill the plug out and tap the block for a 8mm grub screw.

I have come across many of the problems / issues you have mentioned, here is something interesting that I have come across. I have a motor that was redone by the factory in the 80,s that had shims placed under the no.1 main bearing and lined bored to suit, the shims look like a set of big end bearings with the holes for the oil & dowels. I think this was done when the bearing spun & damaged the seating area of the bearing and the line bore had to be redone. The dia on the no1 bearing seating area is about 1,5mm larger than the others. I will organise a pic, have any of you ever seen this?

I have seen those and they effectively turn the case to junk if it needs a linebore again.
Watch out for oversize cam bearings as those are like diamonds to find.
Armand