I have a manifold and downpipe setup with a t3 flanged 50 trim turbo. the exhaust housing is 5 bolt but the downpipe is 4 bolt. Can I bolt up a 4 bolt downpipe to this turbo? my idea is to drill and tap for a 4th bolt since it looks as if from the naked eye, three should bolt right up

Also can you buy a new exhaust manifold with a divided housing and mate it up to a non divided turbo? will you see benefits of the twin scroll or not?