Many Great SW Flying sins will be forgiven if you can stay well under
your gross weight and confine your flying to the early morning and late
evening. It can get choppy enough to pull your molars out during the
day, but the scenery is incredible.

Be sure you have an EGT gage and know how to use it before venturing
into high altitude strips. I agree 120 hrs TT is marginal on the
experience but doesn't rule it out if you are careful.

My most spectacular flight ever in 40 years & 1600 hrs was early summer
morning in a lightly loaded 145 hp 172 from Bryce Canyon to Grand
Canyon.