I find it so interesting that if a person is told something is *****, they immediately believe it and then perpetuate the the info with more misinformation.
Someone tells me something is *****, I wanna know why, I wanna know more I dig and dig and form MY VERY OWN opinion based on a great deal of information and effort to determine what is what. Now sometimes I find out that ya...they where right, it is *****, or oh my, what a sad situation for this person saying things like that if they only knew the truth...
Kid, do the research for yourself, don't take every single word your mechanic/machinist says as fact, learn about the facts and form your own opinion.
Most of us here have seen and done lots and tend to have some history and knowledge to support the opinions formed based on experience of their own and cumulatively of others, and a fine example....BERU vs any other craptastic glow plug. Ya a beru can and sometimes do swell, however it is much less than the autolites champions and any other brands...why? I'm not an engineer to explain it but based on my own observations and those of others the PREFERRED plug is a beru, will others work sure...So cumulative experiences tend to carry some weight.
Good luck I sure hope you can find a set of slugs cause honestly, and engine done right is so freakin sweet it's not funny.
And remember we are here to offer advice with a little gentle

in fun now and then....Your taking on a major project and that's freakin awesome!