Yup, got one for my '68 Catalina. $ 4 $, its the best upgrade I've done to that car. The other "good" upgrades were swapping in a 428 for the original 400, going from a 2.73:1 rear end to a 3.23:1 ratio and swapping out the junk Holley List #3310 for a stock Q-Jet.
For my Mustang it will be mostly the same things: swapping in a DUI, increasing the rear end ratio from 2.79 to 3.25 and finally getting the triple 1-bbls to work!!