Zooropa,
just to show that all engines from the UK aren't junked motors. These guys http://www.turner-engineering.co.uk/index.html do rebuilt engines running from £1950 exchange (about $3000). Obviously you would have to ask them about a non exchange engine but they do ship world wide. They have an excellent reputation for quality here in the UK.They also do perfomance cylinder heads which again have a great reputation. I don't know anything about import regs into the US so that'll have to be something you work out.
All the best
kyle