Telescope efficiencies (main beam and aperture) are given in IRAM Newsletter Nr. 18 (November 1994), in the 30m Manual [10], and are available too on a one page IRAM 30m Telescope System Summary (see IRAM Granada WWW pages, http://iram.es/).
At 1.3 mm (and a fortiori at shorter wavelengths) a large
fraction of the receiver radiation pattern is distributed in an error
beam (which can be approximated by two Gaussians of HPW 
170''
and 800'' -- see
A&A 274, p.144-146
for more details).
Astronomers should take into account this error beam when converting antenna temperatures into brightness temperatures.
Beware of possible interference of the 230G2 LO into the 3 mm receivers. The 230G2 receiver cannot be operated with the 2 mm receiver, since both receivers use the same control box and polarization. Switching from one receiver to the other is not straightforward. Please specify in the proposal form whether you choose to use the 2 mm receiver or 230G2.