It can be done, but I don't recommend it. The case has small oil passages, single relief, no inserts for the head studs, and you can't tap it for full flow filter.
Machining required:
Bore case for 90.5
Drill and install 16 threaded inserts
Drill and tap 5 holes to M8 (oil pump, oil cooler)
Alignbore
You will also need to get a 1500/1600 crank so you can use an o-ring'd flywheel.
And that flywheel will have to be gotten so you'll have it 12V
12V Genny stand needed
Set of DP head studs
If you are going to put $ into a case, you should get a 1600 case to start with.