I was searching e-bay for suitable engines and came across this...
eBay Motors: JDM EJ20 Twin Turbo DOHC 16 valve Subaru 1996 250hp (item 290119074685 end time May-29-07 09:43:46 PDT)
It has the 2wd transmission so it's a front wheel drive setup, do you think that will work in your roadster? I know you'd probably have to have dimensions to answer that question accurately but I think that would be a killer engine to install. I'm getting a big paycheck soon and that's what I want to build!!