The best shuttle service on the Salt River is with Wildenress Aware Rafting. They have the nice office on the right just East of the Bridge at Johnson Village on the Arkansas River and aslo have the nice trailers in the parking lot on the right at the put-in for the Salt.
Call ahead to make reservations at 1-800-231-7238 or use their web form at https://www.inaraft.com/private-shuttle-salt.php
There have been some break-ins in the past at the take-out and it is best to not run your shuttle ahead of time. They will keep your vehicle at the put-in until very close to your take out day. Also, they have a key drop box so you don't have to find them at the put-in.
With snow pack at double the average, flows are expected to be 2,000 to 6,000 for the whole season. Expect flows over 2,000 through mid-May and over 1,000 through June 1. There may even be water in June depending on the weather!