I'd just throw in the DOHC for the test. Bin the EFI and pop on some cheapo bike carbs for £50. Make a inlet manifold for around the same and use megajolt. Thats one perk of the DOHC, it has a trigger wheel built into the crank, complete with sensor.
Whatever engine you use, your going to be spending money on it to make it fit (exhausts, manifolds, sumps and management) So you might as well pass your test with the engine you have got, then throw in something else when emissions aren't a problem
Oh and to answer the LSD question, a RWD 260bhp MR2 turbo only had it as a optional extra, so until your getting over 200bhp/tonne and wanting to go wide open on the throttle out of a corner, I wouldn't bother.