The morgan gearbox goes straight on to the Mazda MZR engine ('cos in actual fact its a ford duratec engine, or the ford duratec engine is a Mazda MZR, depends which way you look at it!)
I have the set up in my plus 4, the 200bhp supersport engine, 5 speed mazda box, great combination, you just got to be sure the mazda VVT cog is of the lates design it can fail resulting in a timing chain like clatter on start up, the later one doesn't, allegedly!.
The gearbox will hold up to 260+ bhp thro it. With 260 bhp out of the MZR/Duratec forged crank and pistons would be required. HWR Motorsport in northumberland do a lovely cosworth engine and get the blocks and heads in half a dozen at a time from US. Omex also do a lovely MZR/Duratec see thier website with prices. They developed the plus 4 s/s engine i believe