Taking bets(no money involved) How long will this engine last?

A friend of mine back in high school ( 1976 ). Rebuilt the engine in his Buick wildcat, everything was cleaned up at the local car wash, he used a ridge reamer, and a electric drill to hone the bores. Oil holes were cleaned up with a barrel brush for his gun, cam bearings were driven in with a piece of wood, crankshaft journals were cleaned up with ultra fine sandpaper. The valve's were cleaned up in a drill press and we used rough valve lapping compound, the valve's were put in the cylinder heads and then we put the stem in a hand held electric drill, this was better than lapping them by hand, the final phase of the valve job was the use of a fine lapping compound. The chamber side of the cylinder heads was cleaned up with a board with sandpaper glued to it. Before he put the engine back together he took it to the car wash for a final cleaning. The only new parts bought were the rings, rod, main,cam bearings, oil pump, timing chain, gaskets. It ran for a good 5 years that I know of. I think that he did a good job considering the money he had to work with as he also was helping his folks out with money.