RAM Part RAM-B-166-GA34U : Garmin makes a great GPS.  However, because of the unusual shape, mounting options are limited.  

If you are looking for the best mount in the industry this is it.  Made of marine grade aluminum, this mount comes with a cradle that surrounds your unit.  This attaches to a mounting system with a heavy duty 3.25 inch locking suction base.  

This includes a custom cradle to surround your Nuvi.

Fits the following Garmin Nuvi models;

1300, 1310T, 1350, 1350T, 1370T, 1390, 1390T, 2455LMT, 2455LT, 2475LT, 2495LMT