I am more of a do-it-yourself kinda guy, I think if you want to spend a little extra money, rebuild. That way you know what is in your engine, and that you are 110% sure that everything is perfect. Plus you get to customize your engine, forged pistons, high performance connecting rods ect.... and the list goes on. If you are a need-it-now- kinda guy, I would stick with the D series but the B series can be fun. Check out http://www.jazzproparts.com/SearchResults.asp?Cat=1 I believe, or something close like that for some nicely rebuilt B and D engines, for about 1500-2500 pending on what you want, and shipping. Enjoy
Mr.Porsche