I know this is an old thread but since there was a lot of discussion on it, I figured I'd add my experience and some video in case anyone is still looking at this system. i know when I was searching around online I would've liked to see more info so hopefully this will help someone else!
I just installed the TBP Stainless headers and this Magnaflow exhaust on my 74 with a 3 speed. Passenger side Headers dropped right in with only a tiny modifications to the charcoal canister vacuum breather line on the passenger side frame rail. Drivers side I had to remove the brake booster, put some new bends in some brake lines, and remove the clutch linkage to get the header to fit. Not the end of the world, but not a drop in. The back end of Magnaflow exhaust installs nice and quick. I have a standard rear tank but I don't see that there would be any fitment issues with a 23 gal. The rear exhaust hangers bolt into the prethreaded holes in the frame on either side of the tank in front of the support strap. A deeper tank wouldn't interfere (it doesn't look like). it should be noted that I just did a 1” body lift and had to move the stock e brake cables over the frame rails so they wouldn’t sit on the mufflers. Not sure if this would still be possible with out the body lift. The hangers on the back side of the mufflers bolt through the frame crossmember just behind the rear diff, and again without a body lift this might be a bit more difficult, but should still fit. I was surprised that there are no other hangers on the front half of the system and the weight of anything forward of the rear differential hangs on the headers. I think I'll probably add a hanger to each of the front of the mufflers to be sure it doesn't sag over time.
I don't see any issues if you need to access the transfer case but I am concerned that I'm going to have issues when swapping to an AX15 later this year. Theres not much clearance from the transmission crossmember (about 1/4”) and I know the AX crossmember sits lower. Might need to make a custom crossmember.
As for the intermediate pipe needed to connect the headers to the X pipe, It was about a 12" section with a 30 degree bend to mate them. I don't have a pipe bender so I just drove it to the exhaust shop and had them do it. What a fun trip that was with open headers.
The 409 stainless isn't anywhere near as good as 304, but since Im in southern California, corrosion isn't an issue. I’ll add some videos soon for sound, but at idle it sounds great. My truck has a Jasper 302 Class 1 crate motor with a mild cam and an Edelbrock intake and 4 barrel. Nice and throaty while idling, but not loud. Anytime I put my foot in it the sound responds and it loud enough to turn heads, but not annoying or raspy. At 55-60 mph theres no drone at all. And my truck is rhino lined all throughout with a hard top and no dampening/sound proofing. Exhaust aggressiveness in relation to sound I’d say 5-6 out of 10.
I hope this helps others if still thinking about this setup. I paid Under $300 for the stainless headers, and $709 shipped for the Magnaflow exhaust so not cheap, but I feel like a good deal for the whole setup with a relatively ease of personal installation. Considering I do all the work to my truck myself, I’m always down to pay a little extra to save some time under the truck, especially since I’ve got piles of new parts in my garage still waiting to get installed.
If anyone is a SoCal resident I’ll be at FFF on April 15th at Knotts Berry Farm with my truck. Would love to meet other owners.
