I recommend you fix or replace (FOR) what needs fixing or replacing and 'use as is' those parts that don't need FOR. That's what the factory calls for. Why spend more?.. so you can let it set for another 15 years while you put 800 hours on it and corrosion is your biggest unseen problem? I also think anyone blowing oil out the motor seals and crankcase machined interfaces needs to investigate and see if a simple crankcase vent/oil separator replacement may fix the problem. Too much crankcase pressure will always blow the oil out past the rings into the combustion space or out the crank end seals, cylinder base joint, etc. That's why racing engine builders use vacuum pumps on crankcases to pull negative pressure on the case and reduce pumping losses and reduce oil consumption and blow by - it's one of the best kept secrets in engine building for a bunch of reasons.