data dev recommendations sought for geology layer

I'm digitizing a 1:500000 geology map which only has lat/lon coordinates
ticked off on it (best I can find). I've enlarged the map to facillitate
digitizing. Documentation for the map indicates that a 1:250000 quad map
was used to compile during mapping.

I'd like to digitize the map into a utm database location. It has been
recommended that I use the program m.ll2u to capture 6 utm coordinates from
the lat/lon ticks to use as registration points (using the clark66 spheroid
parameter).

Can anyone offer some constructive criticism on this procedure and recommend
what grid cell resolution (and dimension) I might use ??

thanks,

D. Youngs
ASI, Las Cruces