I'm not sure what you mean by '9.1 is 68k also'. Mac OS versions 8.5 upwards required a PowerPC processor, i.e. they won't run on a 68k machine. However, that doesn't mean they can't run applications written only in 68k code - for example, I still happily run Word 5.1 under Mac OS 9.0.4 on my Powerbook G3!
Also, a quick search of the NI site for "labview 3.1.1" mac brought up at least one reference to a PowerPC version of this version of LabVIEW - but it appears there were separate 68k and PowerPC versions, so it may depend which version you have. Again, it's not necessarily the case that the 68k version won't run on a PowerPC machine, just that the performance won't be optimised. Remember also that there's a difference between "compatible" meaning officially tested and supported, and "compatible" meaning it doesn't crash. It may be a case of just trying to run it on whatever Mac you have and seeing how you get on.
