A friend of mine had alot of trouble with Volkspares exchange engines in his Beetle. I think he had at least 4 replacements before getting a partial refund and going elsewhere.
My '72 Beetle on the other hand had one of their Gold engines with new VW heads 40,000 miles ago and is still running like a dream 10 years on.
I seem to remember my friends problems were all head related (cylinder that is, not his own), so as long as you go for gold you should be OK.
