Will this PB Booster fit & work on a 65 Barracuda

I've used them but you have to modify the support struts (which I don't see in your photo). If you don't use them, the booster assy. will move around and eventually crack the firewall. Naturally, he'll need a different proportioning valve and lines to go with it. It's not a straight bolt-on unit. If he's keeping the drums on his car, you'll have to change the master cylinder too.