www.classiccarstereo.com $ 74.95 w/out speakers. Made for 6.5"
www.classicparts.com $128.95 w/ 5.5" speakers
I am sure LMC has some cheaper, but I don't shop there.
I eliminated the vents on the '65 ( I am adding under dash air) and used them as the speaker enclosure-just making a flat cover with the speaker mounted into it. I didn't want my speakers mounted as low as these pre-made ones where they'd get hit.