GJohnson...I currently have three 4-speed 350 69 cars...two with headers. I've tried Hooker Comps, Dynomax, and Hedman...all long tube, all 1 5/8's inch diam. Here's my experience.
Dynomax Jet Hot...(coated)...the #6 spark plug clearance is a joke. Even with a shorty plug, you'll still be changing out blistered plug wires frequently. But they clear the reverse lock-out linkage...only one of thtree that does. The clutch pedal spring has to be re-routed. The flanges are ok width...about 5/16's I guess. Tubes are 18 guage steel. Very shiney coating...almost chrome-like. Uses a 7/16's socket(s) or wrench for install. They have about a half inch more ground clearance than Hookers and Hedmans. Good price.
Hooker Comps...ok, but very close to the steering box, needlessly close to the starter. Won't clear your reverse lock-out lingage, but clears the pedal linkage fine. Pedal spring has to be re-routed. Thicker flanges than Dynomax (I believe). Fair plug clearance all around. Uses 7/16's socket. I can't speak to their coating...but I'm sure it's available. Most expensive of the three, but not bad.
Hedman Elites...best plug clearance of the three. With 90 degree plug boots, no pipe is within 1/2 inch of the wires. Nice! A little more room around the starter. Won't clear the reverse lock-out lingage, but you can use the stock clutch spring and location. Good thick flanges. Uses 3/8's socket for install (a little easier). 16 guage pipes (I believe). Nice looking coating...more aluminum looking than chrome.
My opinion...I strongly endorse the Hedmans.
Three quick pieces of advice...
1) Get coated headers...the benefits far outweigh the cost (about $200 more)
2) Don't use the gaskets provided by any of the three. Go get some good quality header gaskets and collector gaskets.
3) Remove the entire clutch linkage first...will save you time.