I don't know anything about the company, but I thought the engine heretics might find this interesting - BMW e39 M5 (S62) engine for sale: http://www.rennwerks.com/M5%20Motor.htm
Complete with gearbox although that will be no use in a 40. For those of you that don't know, the engine is a 4941cc quad cam V8 with vvt on both intake and exhaust = 400 bhp and 369 lb/ft. Very flat torque curve.
It's good fun in my 1800kg M5, so could be amusing in a 1100kg GT40. Probably far too expensive an option though - you could build a superb Ford for the same price.