Ok, in theory you could hack a rom dump to do "anything" you want it to do. However, rewriting the game without the source takes a considerable amount of time and effort to do, and if you want to actually play what you make on a real 64 you'd either have to find some sort of specialized cartridge or figure out how to print your data to a cart.
If you're looking into just playing the 64 cart faster, you can look into overclocking your N64. However, modifying your system may damage your system or cartridge, and is possibly against SDA and SpeedRunsLive rules.
If you're looking into playing Ocarina at a higher framerate on an emulator, you would have to edit the uncompressed rom. You might find something about it on
http://z64.spinout182.com/