I can't remember the first gear ratios, but aren't they both non-sincromeshed first gears? My only thought would be getting gears for the T-18 would be easier down the road than the T-98, but I can't remember if they shared any parts. In the past I was looking for a T19 to get the sycromeshed first gear even though it wasn't as low of a ratio.
I found this https://www.novak-adapt.com/knowledg...ssions/manual/
under the 4 gear transmission it has a pretty informative explanation for T18/19/98, though the T98 has its own section to review. I don't recall seeing it before, so it may be new to you as well- gonz
Come and take it
Go work at joann fabrics if you can't shoot a gun