The core support is the (metal) framework that holds the radiator in place. This should be true on all vehicles that I know of.
Short answer is NO.
take one end of your heater hose off the heater core and run it back to the intake port.
On my 96 Century and 68 Eldo they mercifully put the fan, case, and motor under the hood, on the firewall, on the passenger side. It comes apart with probably a 1/4" socket or nut driver. I'd guess it's the same on your car.
I've had five or six sixties Buicks . I love em , I have a 63 Riviera and a 68 Skylark .Any shop that works on classic usa gm cars can work on that car . If its rusty don't buy it ! ;)is it expensive and a big hassle trying to find parts for it?Yes ! :)Its kinda tricky to find some parts for those cars a car with a Chevy 350 would be way cheaper and easier to deal with but its not a Buick which is part of why its a cool car . If your car has a Buick 430 V8 in it that's my favorite Buick motor . I used to get what looked like 14 mpg around town and nearly 22mpg on the highway in a 1969 Electra 225 ltd 4 door hard top . And it was fast as you'd ever need it to be . I'll buy another one and I just finished getting the 430 from that Electra built for my 68 Skylark .Good luck .
Try the driver side core support on the engine side. That's where my 68 is located. Sorry I couldn't be more specific for your year of 'Bird.
It is 18 gallons/68 liters.
The fuel tank capacity is 68 liters/18 Gallons.
I think 6x9's would fit in the back. Try Crutchfield.com.
It is rated for 150 pounds, which would be about 68 kilograms.
You may want to look at my answer posted under 1996 Buick Park Ave Belts the owners manuel has diagrams on pages 6-67 and 6-68.
68
68/100 x 100 = 68