The A to Z integers cannot be referenced by Index. It is not supported by the compiler. If you wish to use 32-bit integer array, try the EMLINT[1] to EMLINT[16]. These are 32-bit integer array that you can freely use in your applications.
Unlike C or C++ language, there is no "type casting" support in the TBASIC language. You can still convert between Strings and Integer using the HEX$, STR$, VAL, HEXVAL functions. When a 16-bit number is assigned to a 32-bit variable the contents are converted (and sign-extended) automatically without the need for casting. Likely when you assign a 32-bit number to a 16-bit variable, only the lower 16-bits of the 32-bit number are assigned to the 16-bit variable and the upper 16-bitsare dropped automatically, again no type casting is necessary.