How can we calculate the R&R to a gauge if the process where is used only has unilateral tolerance? i.e. min 35 Lb-in

In the R&R process, the values are recorded and tabulated, the result is expressed as a percentage of the total tolerance. If the Low end of the tolerance is "0" and the high end of the tolerance is (-35) the absolute value of the total tolerance is "35". When the R&R Values are computed, squared and added together, then the square root is taken and divided by the tolerance, the resulting number is the gage R&R percentage.
10% is excellent, 11-30% is acceptable based upon the application, but should be closely monitored, and 31% or greater is unacceptable.

Understand what you say, and that work if you have only specified the limit at the high side of the spec, but what happen when you have only the low side of the spec.?

Perhaps you could use the actual error as a guide. When you calculate a GR&R, you get 2 values, the actual error and a percent of tolerance. With respect to your minimum requirement of 35lb-in, if the actual error in your R&R in this case is say 3lb-in, and you can demonstrate that your process is capable to +38lb-in minimum, then the actual gage error of 3 will not cause you to accept bad product. Sign it off and make parts.