question about aftermarket radio? ways to secure it better?

[chevytruckclassics]

so after days of debating with myself, i cut the dash in my 1967 k10 for a new radio. the bracket the holds the radio fit mostly snug in the hole, but it is a little lose and the radio can but moved a little. I put a piece of foam between the bottom of the radio and the ashtray to give it a little support. any idea on how i could secure the radio better? any suggestions would be appreciated. Thanks!