In case you are still looking for information, traditionally 27 series EPROMs are used to make new cartridges. There are a lot of different options though, if you are just looking to test on real hardware. Some are:
- Starpath/Arcadia Supercharger: RAM cartridge from back in the day with a cassette interface which can be hooked up to a PC's headphone jack. A program called makewav is used to turn 2K or 4K ROMs into an audio file that you play which the cartridge translates and downloads to the RAM.
- Cuttle Cart: This is a now somewhat rare homebrew cartridge that is similar to the Supercharger, but the RAM is 64K and it supports many bankswitching methods. Not being produced any more
- Krokodile Cartridge: a flash cart that communicates with an RS-232 serial port. Supports 512K ROM and 32K RAM if I recall correctly. No longer produced.
- Harmony Cartridge: a 'flash' cartridge built around an ARM microcontroller. From what I understand, the MCU monitors the address bus and supplies the data bus with the correct byte. The MCU can also offload tasks from the 6507 and assist in various ways. 32K ROM, 2K RAM. Still produced, website here:
http://harmony.atariage.com/If you want to hack up an old PCB and use (E)EPROMs, the original Atari mask ROMs have the same pinout as a 2532 but are active high rather than active low.
You should definitely check out AtariAge as suggested, there's a lot of great info and people willing to help you out.