You got hold of someone at Wiseco that didn't know their *** from a hole in the ground.
https://www.campbellenterprises.com/slant-six-6-performance-parts/wiseco-225-slant-6-six-pistons.php
And about the hydraulic comment I made. It's my personal opinion that the slant 6 was never designed as a hydraulic lifter engine. They do not even have oil galleries to pressurize the lifters. The lifters are fed oil "backwards" through the head, through the rocker shaft, through the rocker arms, through the pushrods and FINALLY to the lifters. It's simply a piss poor design IMO for a hydraulic lifter engine. Are you actually saying you're afraid of a valve adjustment once every couple of years? Because that's about the frequency even if that.