I'm amazed at how many full size 65-66 B bodies I see in US wrecking yards as well with no power brakes. I've seen many air conditioned full size Chevys with A/C and no power brakes!
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
I think my first 5 or 6 cars (or more?) didn't have power brakes. I got so used to the pressure needed and the brake feel that I didn't like driving anything with power brakes after that. Not to mention almost putting passengers through the windshield when jumping into a power brake car after not having driven one for awhile...
I still prefer a harder brake pedal to one with lots of assist.
'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.
The tach was standard equipment in all Canadian Pontiac 65-66 B bodies with a 4 speed, regardless of engine. I always thought it was the same for US models but a guy showed me documents for his 65 4 speed car and no tach. I scrapped a 66 2+2 421 3 speed manual car in the 80's. It had a tach and I found the build sheet/option list under the seat showing the tach but it never registered that since it was on that sheet it was an extra cost.
I bet it's a dealer installed power brake booster. In those days it was quite common, there is a part number for a power brake accessory kit.
My 65 Canso SD was built with power brakes and power steering. I have the paperwork from the dealership showing both of those options were removed before delivery because the lady wanted manual steering and brakes.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars