Dave, be careful to look at the condition of the base before you buy that thing. If it is rusted or dinged up, pass.
A Starett 98 is a good level but, in my opinion, lacks the sensitivity you need for leveling machines. I own a 98-6 and I use it but only to get me in the neighborhood so I can use my more precise level.
What is the difference? Speed. A precision level will get you very near dead level very quickly. You still need to do a 2-collar test to finalize your level regardless of the level you use but a precision level will usually get you within 1/8 turn of a leveling bolt of foot.