Thanks for all the input guys!

Jmac: Excellent information - Thanks very much! I've tried similar methods to the one you presented. Your method produced the same length and slightly larger diameter than the method I've used previously.

Datto1000wagon: They look like a decent set of headers. They are the shortest shortest primary length I've seen on any 4-1's for a Datsun.

My gut feeling is the same as yours, Benny & 1000coupe. 4-1's are for the track and 4-2-1's are for the street. Thats the main reason why I'm kinda snobbing the JTS units at the moment, despite all the good reports they get on this website.

Got a price from the manufacturer, 'Liverpool Exhausts' for the hurricane 4-1's. They are $250 direct plus postage (which sounds really cheap to me). He's going to give me the diameters and lengths tomorrow. I'll post them up when I get them. Oh, and the Hurricane headers are Mandrel bent, unlike the Hi-tec's.

Also, just to clear the air for others, the parts Stewart Wilkins Motorsport sell are the JTS items.