I bought an A1000 earlier this year and it was a US model. I need to use a 240/120VAC transformer (why can't everyone use 240VAC?). Once when I run Sysinfo it reported it as a PAL machine with a 68010CPU (IIRC). I was confused! I opened it up and it was a big expansion board in there that gave me a total of 1.5MB RAM.
I can check again if you are interested and maybe open it up and have a look. If my A1000 is a pal machine then it is proven they can be modified.
Edit: I think this is the board that is inside
http://www.bigbookofamigahardware.com/bboah/product.aspx?id=990
