Not trying to be a smart azz here.......but whether you are "sold" on it or not, that motor is NOT sealing. It pumps a lot of oil and that doesn't come from the seals. That is by the rings. The bores are either too big, not straight, not round, the rings just never seated.......or all of the above. If it was sucking oil in the ports, it would smoke. By the rings, not so much.

The pistons that are "somewhat" clean near the top, that is just a function of the quench and where it makes enough heat to burn the oil off. Number 4 is cold. That cylinder makes no power.

The motor could have ten or 1000 passes. Carbon is black, but it's dry. Oil is wet and shiny..........that's what I see.

Opinions are like..........well you know........and everybody has one, but I am a firm believer in both alum caps and hard block in cast iron motors. Obviously ALL the machine work has to be done AFTER the pour. Factory cylinder walls can be thin. The hard-block is to KEEP THE BORES ROUND. They don't stay round, it will NEVER seal

And those heads are in SERIOUS need of some new valve and a decent valve job. Can't be any margin there and they are WAY deep