I would think twin hx35's would be a bit big but don't quote me. Turbo mustangs has some good information on junkyard setups. Did you build the bottom end of that mark engine or just throw it in stock?
There is a guy on here running an hy35 (slightly smaller than hx) on his 3.8 and boosting under 2k if I remember right. I suppose it all depends on how you want to build the boost. http://www.turbomustangs.com/smf/index.php?topic=4365.0
I thought I read about a guy running a bigger HX single turbo with good results.
If I was going to build an engine I would stick with the aluminum block and a cobra crank.
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