The floorpan should already be drilled for the seatbelts.  Crawl under and you should see the holes, they'll likely have plugs in them. 

Your '64 will not have predrilled holes for rear seat seat belts

WE   can soon send you photos of the rear locations and a drill bit or 2  

Indian wrote:

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Your '64 will not have predrilled holes for rear seat seat belts

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 But there is 4 dimples in the floor pan where your should drill. These locations are easily accessable from under the car for large fender washers and lock nuts.

Congratulations. Your belts look great. I do like the added safety for passengers.  I always found it odd that GM installed them in the front of my '64 CS but not in the back.  I suppose the rears were your typical option.

Even the fronts would have been an option in 64 wouldn't they?

Now you have me wondering....!

You may be correct although I have often wondered about the accuracy of brochures. The following is an article I have quoted from "Automotive News."

I suppose one can find a plethora of articles on this topic. Ironically, the days of getting a simple answer appear to be history.

"Automotive safety reached a turning point in the 1964 model year. That was the year front-seat lap belts became standard equipment in passenger cars.
Automakers had seen the writing on the wall - or, rather, on the books. Twenty-three states had enacted legislation by 1963 requiring seat belts in front outboard seating positions for all new cars.
'So many states had adopted the requirement, it would have been silly for car companies to make a distinction between the markets that had required seat belts and the ones that had not,' said George Johannessen, a consulting engineer with OmniSafe Inc. in Rochester Hills, Mich.
Factory-installed seat belts transformed seat belt manufacturing. Before 1963, most seat belts were produced in small quantities by about a hundred small producers for aftermarket sales. After 1963, the business was taken over by a handful of well-established suppliers, said Johannessen, who wrote a historical report on seat belts for the SAE in 1984.
The occupant restraint business has evolved into a $4 billion a year industry today, with eight manufacturers of complete restraint systems and about 40 producers of components, reported the Automotive Occupant Restraints Council.
Seat belts were first used in 1885 to prevent ejection from horse-drawn carriages. The restraints were used later on airplanes and race cars.
Automotive safety belts became standard equipment in rear outboard seats in 1967. In 1968, the federal government required seat belts in all forward-facing seats and ordered that shoulder straps be installed in front outboard seats.
SAE estimates seat belts cut the number of crash fatalities 50 percent and reduce serious and severe injuries more than 60 percent. So why did it take so long for the belts to become standard equipment?
First, there were no specifications for making the restraints for many years. SAE introduced some specifications in 1955. Manufacturers of occupant restraints formed the American Seat Belt Council in 1961 to establish uniform production and quality standards.
Some of the systems marketed by small producers were unsafe, said Volvo engineer Nils Bohlin in a taped interview before seat belt standards were introduced. Bohlin invented the one-piece, three-point lap/shoulder belt in 1958. The 1959 Volvo was the first car to be fitted with the three-point lap/shoulder belt as standard equipment."

It is interesting that your '64 Tempest convertible had front belts. Do you think that there is any chance convertibles came with front belts before hardtops, sedans, etc?

I think front seat belts became law for 1966 in Canada. Carl, do you have them and are they listed as an option?

-- Edited by DonSSDD on Tuesday 13th of November 2018 04:57:44 PM

66 Strato standard equipment front and rear it says.

I thought it was 64 when seat belts became mandatory. I remember getting pulled over in the 80's and the cop asking if I had my seat belt on(63 Caddy/no belts),told him the year and he said good thing it's not a 64. So I took it as 64 and later seat belts were standard in all cars? Maybe it was,if the car came standard equipped with seat belts in 64 you had to wear/have them but wasn't legislated that all cars must have them until 65?