I've been installing these Audovox units on my vehicles for years. They are frequently on sale for less than $100. I have installed them on my 57 and 58 with the servo under the dash and the noise was never a bother.
http://www.jcwhitney.com/autoparts/Product/tf-Browse/s-10101/Pr-p_Product.CATENTRY_ID:2001597/showCustom-0/p-2001597/N-111+10201+600000566/c-10101
