The weak point is the differential from what others have experienced. Steve H has blown them up with his potent 1500. The launch is the issue. In regards to buying an engine for $4000, that is cheap considering 240 bhp. Do you really think you'll get anywhere near 200 without spending the same amount? Remember these Betas "only" made 120 factory, but you're going to be 100 lbs minimum heavier so what's the point if your not going to push 150+. You'll need the transmission as well. Use Steve C's link
http://www.turbo124.com/forum/viewtopic.php?f=10&t=846&sid=d50953be82aa7cf01c6e23c509322dda as a good starting point.