How much HP for my 360 build in my '67 Cuda

The XE284 is going to be too much cam for a compression ratio less than 9:1. The engine is going to be quite doggy below 3000 rpm and the stock exhaust manifolds will limit the power where the cam will start to work. You will also require a convertor with quite a high stall speed to make it driveable.

A much better choice for a cam would be the XE262 or XE268.