Sorry it’s a bradley gt2e very early electric car based on Vw beetle running gear and fiberglass body
Thanks - that makes the situation much more clear.
Bradley GT II
I'm still not clear if you have a GT II (gas engine) to convert, or a GTE (Bradley factory EV) to update.
So it's light and small... and doesn't have much space for battery. Any of the recent VW Beetle projects would provide an example of potential battery choices. At least one conversion company uses a stack of Tesla Model S/X modules behind the rear seat in their Beetle conversions - only a fraction of the full pack - as a low-voltage (by modern EV standards) battery.
To properly select a battery, you need to think about what operating voltage will work for you, how much power you need to get out, and how much energy you need per charge. The voltage will depend on various factors including your preferred motor, and even half of any common modern EV pack will provide enough power to match the performance of the gas Bradley GT or GT II (and beat the GTE), but 100 miles is a lot of range. It might need roughly 20 kWh of battery, which would be an entire Chevrolet Volt pack (a common salvage battery choice).
I ran across a listing for an EV conversion of a GT II done several years ago with a conversion kit:
1979 Bradley GT II Converted: “EV1E”
It uses prismatic lithium cells from CALB, not a salvaged production EV pack... but it has 27 kWh of them. An entire Leaf pack reconfigured for half the operating voltage would be a relatively direct replacement for the CALB cells.