Q: I was thinking about putting a B&M shift kit in my 65 Thunderbird would this make proformance better

Shift kits typically work by upping the line pressure in the transmission to each gear set. The increased pressure makes for faster and firmer shifts. You’ll probably feel a little kick in the back with each shift. Quicker shifts will make for slightly quicker acceleration but it’s not going to shave seconds off the time. The last car I owned where I installed a shift kit had some engine modifications as well. With the added power and shift kit installed, it would actually chirp the rear tires on the 1-2 upshift during hard acceleration. But like I said, that was with the engine making a bit more power than stock. If your engine is stock, you will probably just get the firmer shifts. If you’re a "car guy" you will like the difference. Just make sure to to a full transmission service while you’re in there.