Preliminary questions about engine conversion

[Bishop]

I have been considering converting my car to a hydrogen system, not not some hokey ebay bullshit. but the problem is, they do not recommend using the system on an engine with a higher then 9.5 to 1 compression ratio. I have a 2007 Yaris, its all stock. So the engine has a 10.5 to 1 compression ratio. The issue is because hydrogen burns much faster then gas, which can cause predetonation at higher compression ratios. I am hoping that because the engine is aluminum instead of cast iron it may not have the issue as much? If not, any ideas as to what would be a good engine to swap it with that has a 9.5 to 1 ratio (or lower)?