E-TTL II is a minor software update for E-TTL. Source: https://en.wikipedia.org/wiki/Canon_EOS_flash_system#E-TTL_II which says:

E-TTL II is a software improvement on E-TTL and is now a standard in all EOS cameras introduced with or after the Canon EOS-1D Mark II in 2004. E-TTL II is implemented in the body, not the flash unit, and therefore can use existing E-TTL flash units and EF lenses.

The main improvement of E-TTL II is that it gives a more natural flash exposure, by being able to handle tricky scenes where the old E-TTL system would normally be thrown off. Such improvements are possible because E-TTL II incorporates lens-to-subject distance information in its calculation, where available, to assist in determining an approximate guide number for flash output. The flash metering system is also no longer linked to the AF system, whereas in the old E-TTL metering, bias is given to the selected AF point. Rather, E-TTL II compares the ambient and the pre-flash light levels of the scene to determine where the subject lies, in conjunction with subject distance information if available. This gives the photographer the flexibility to lock focus and recompose the scene without fooling the flash metering system. 'Hotspots' (areas of high reflectance) that would normally throw off the flash metering system are also ignored in the calculation.

Thus, you are able to use all existing E-TTL flash units with E-TTL II. I assume the converse is also true, i.e. E-TTL II flashes/transmitters (which are just the same as E-TTL flashes/transmitters, as the "II" part is done in the body) should work on E-TTL bodies.

Do also note the film camera's capabilities. Some are only A-TTL, and some others may support E-TTL but may lack certain features (example: EOS 300V lacks flash exposure compensation although it supports E-TTL).