Replace Rims and Studs...for the correct combo

Thick spacers, adapters, and long studs can lead to catastrophic failure. Best bet is to get wheels with the correct bolt pattern (no adapter needed) and the correct offset (no spacers needed). Assuming you do not have a 5 x 4" bolt pattern, there are hundreds of 20" wheels on the market that will bolt onto your car without spacers and/or adapters. If the car does have the 5 x 4" bolt patterns, change the hubs & axles to 5 x 4 1/2". You're going to need bigger brakes anyways, and this is a perfect opportunity to upgrade.