Yella Terra exchange heads used to be done with 0.005" oversize valve stems, I think you can still get valves with oversized stems but not as common....
Big tool fan too, big also like my 90's alternative stuff, spesh the aussie stuff that just kicked ass back then. and even get into chemical brothers...
Sorry to hear that, I hope it works out ok with your mate working for you, losing a close friend without warning is a tough deal for sure. I lost one...