Welcome to the site NamelessJoe.
I think that some people put the the small Buick aluminum V8's in those Sunbeams. As well you might be able to put a Ford 289 in it like they put the 260 in the Tiger. I am sure someone on this site (probably from across the ocean on the island or continent) will have direct knowledge about putting a V8 in your car. Good luck with your build.