Very large dataset

Anyone on here have experience using the CLI script bundle trying to get the best compromise in regards vertex/poly count and take it into unreal, Highest quality poly model is 1Billion tris, splitting it up so each part is about 15m, (64’ish parts)using the scripts and bringing it into unreal with the import scripts, using 128ram, 16gig graphics card, always crashes.
Now, am no fool, and realise i am asking a lot, but can happily bring in a 30m model using nanite into unreal, the script is supposed to bring in each part, convert to nanite, and move on to next part,
any suggestions
my next step is to halve the total verts, and try that, but be real nice to bring in at a higher rex