header advice please??

alright i am looking at two different types of header built for my car/engine setup. the engine setup will look like this. the 1st set are equal lenth headers with 1 5/8 primaries and 2 1/2 collectors. the 2nd set are shorty headers but have 1 3/4 primaries and a 3 inch collector. I was wondering what power range do the smaller primaries start to hold you back? this is for a 383 w/ 150 nitrous shot. thanks for any help .

Generally, shorty headers are a compromise, and sacrifice power to get a compact package.

Go for the equal length header. The tube diameter is quite large enough. Larger tubes are not always better. Slightly smaller tubes help maintain or increase exhaust velocity and are especially good at boosting mid range power. Generally, huge tubes kill low and mid range power in exchange for very high RPM power.