Not knowing what you will end up with for an engine, here is my recommendation on what to have your brother-in-law build for your birthday. First, a 4-1 with a Burns stainless steel merge collector
http://www.burnsstainless.com/MergeCollectors/mergecollectors.html Use the burns computer program to determine the correct dimensions of the collector ... the computer program is free when you buy a merge collector. (you did say it was your birthday)
The primary tubes should probably be 1 3/8" tubes... that will give you the best all around street performance. Go to 1 1/2" tubes for more top end HP (above 5000 RPM). The primary tubes should be 36" long... now here's an important part... all tubes should be (within 1/2" max) the same length.
And since it's your birthday, a two stage header would be really "trick". The first section of primary should be 1 3/8" tubes about 18" long (all 4 the same again), and the second section of the primary should be 1 1/2" tubes about 15" long. If you "build" your engine, increase the diameters one tube size.
The diameters and lengths biven here will vary a little from engine to engine, and according to engine specs (carb, cam, valves, porting, etc), but this will work well 95% of the time on 95% of the engines. For all out racing, contact me.
By the way, I suspect that Rally Bob may have a little bit different numbers that are valid. That's the way it is with engine builders... different folks use different "tricks". Hopefully, Rally Bob will give you some more insight.
Happy Birthday
