90 degree oil filter adapter oil flow

I've heard that 90 degree oil filter adapters cause some restriction to oil flow. I've also been told that they will flow better after some modifications .Since I've never done it before I'd appreciate it if you give me some general ideas as to how to go about doing it.

I know that straight adapters flow a lot better especially after drilling 4 extra holes on the plate.Unfortunately I can't use a straight adapter due to interference issues with the exhaust manifold.

My car is a 72 challenger 340 with the HP exhaust manifolds .


Thanks in advance.