I used to have an "IDE" called "Develop 64" that had a 6502 assembler and disassembler (6510 actually). Anybody else remember that? It was pretty good for its time.
I have fond memories of capturing an interrupt and displaying the time in the upper left corner of the screen without blocking the command line. Good times!
There's no difference in the instruction set between 6502 and 6510 (at least not in the documented opcodes) - the 6510 is a 6502 with up to 8 GPIO pins and a tristate address bus. On the C64 the IO pins were used for bank switching the ROM and underlying RAM, and for controlling the tape port.
(fun and useless trivia about the tape port: you could use your C64 as a very primitive 1-bit sampler by recording the tape input, and play it back by toggling the input to max and down again on every "1"; with some basic run-length encoding you could get a reasonable length sample in memory and still be able to record at a tolerable sample rate to get recognizable output)
I have fond memories of capturing an interrupt and displaying the time in the upper left corner of the screen without blocking the command line. Good times!