Hey, good luck with those.
I don't have a longtube story, but I'll share a similar experience.
When I dropped the motor in my car, I did so with the stock shorty headers bolted up (didn't have the BBK's yet). As I was trying to bolt up the H-pipe (also stock, but hollowed) I ran into a problem with the passenger header flanges meeting up with the H-pipe (bent flange). I worked on the thing for two hours. Of course, there's absolutely no room to work with on that side, and I cussed, grunted, and sweated using long screwdrivers, prybars, and hammers.
After a lifetime of lying on my back with my head rolling in that kitty-litter spill soaker stuff, I gave up. I finished putting it all back together and decided I'd give it one last try. I crawled under, took a long screwdriver, tapped the bracket once, and it slid right on. Oh...I was pissed. Two hours struggling with it and all it takes is one little tap a couple of hours later.
Remember, the hard stuff goes just fine. It's the easy stuff that will eat your lunch.
--nathan
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'91 GT, Coast 347, 9.5:1 compression, full intake, Wolverine 1087 cam, exhaust, Keith Craft ported Windsor Jr. Irons (235 cfm intake, 195 cfm exhaust), AOD, PI 3500 converter, Lentech valve body, 3.73's (4.10's in the works), and Yokohama ES100's out back.
Daily Car: '04 Infiniti G35 Sedan 6MT