Was your mechanic looking at the shop manual when he worked on it? Or was he just using normal machining clearances ? Did he know the first bore is a different size from the others ? Did he measure and bore each sleeve to the Respective piston which was going into it ?
Oil usage can be valve stem seals... but excessive blowby is pretty much a rings deal...
Did you measure the oil usage starting from when you got it running again ?
If you were to put in a 5 cylinder I would sure suggest using a NON turbo....to keep some of the wonderful working room in the engine compartment..
Going from Lubbock to Anywhere your engine will turn over a couple of million times... and the point of most action is the rings and sleeves... so when looking at 25 year old cars what you are experiencing is not that the rings wear out faster than usual.. but that the rest of the car survives better .... You don't notice the rings and sleeves on those cars which have already been crushed