Chris,
You really don't have to lay your own OO scale track or look for GarGraves products. I have a small collection of Hornby OO two-rail scale trains manufactured around 2010- -loco & tender and passenger cars. They run just fine on HO scale track [in my case, Trix]. Your vintage Lionel three-rail OO scale trains would probably run well on Marklin HO trackage.
Bob G.