Yes, 275 65r20 tires will fit on a Silverado 1500, is the quick answer to your query. The answer to the question of whether it is a good idea to choose this size is not necessarily no.
A Silverado 1500’s factory standard tires measure 31.6 inches in the form of 265/65/R18 and 33 inches in the form of 275/60/R20. This indicates that you can fit an additional inch or so, although doing so is not advised. If you are running stock suspension and are unwilling to perform trimming and cutting, you should be limited to 33.5-inch tires at most.
In general, it is advisable to stick with the tire size recommended by the manufacturer. This will ensure that your Silverado 1500 has the highest possible performance and riding quality. In addition, larger tires might place additional strain on your suspension system and reduce your vehicle’s stability on the road.
Consequently, while 275 65r20 tires will fit on a Silverado 1500, it is not recommended. If feasible, it is better to comply with the factory-recommended tire size and avoid larger tires.