Pipe Size?

I am swapping my 225 for a 360. The slant had a dual exhaust system with 2 inch pipe all the way back except for the mufflers which are 2.25 in and out.

For the 360 I have 340 exhaust manifolds with 2.5 inch head pipes. My question is, if I keep the 2 inch pipe after the mufflers will it make a big difference in horsepower. The system is all mandrel bent stainless so I would like to use as much of the old system to save $$$ if possible.

I read going down to a smaller pipe after the mufflers helps speed up the flow but I am not sure if going from 2.5 to 2.25 mufflers then down to 2 inch pipes will work and sound ok? Thanks for any input

Brent.