I think you could get some holes to line up. You would probably need to tig some alloy blocks on the bell housing for the remaining holes, redrill the block with new holes using an A series sandwich plate to locate bolt and dowel positions.

For the engine, I would seal of the stock CG dissy drive and fit a good crank trigger system like the Electromotive one (if using carbs) or just make up a Hall trigger system if injecting and using an after market ECU.
This will allow you to get back close to the firewall. The stock dissy isnt mod friendly.
One of these engines in NZ made 165 hp with forgies, cams, good pipes and a motec ECU. He had a modded sequential box behind it in a rally car.

The fact that you can carry the whole engine (58 kg's) makes it a great engine for the 1200 and lighter than the A series.