I just disabled the lockout on an American console. The reason it runs slower on PAL consoles is because of the system outputting 50hz, usually the ROM in the cartridge remained unchanged, which is why it runs slower. Some games tried to fix this, like Super Mario Bros, which actually runs faster, and Mario 3, which had the audio corrected. Castlevania seems to have been left unchanged, but I don't know if any revisions were made to it before being released in PAL A countries that I haven't noticed, or which version was released here.

Is there any major difference between the PAL A and the American game? For example, if I play the PAL A release on an American console would there be any difference between that and using the US release?