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Mazzolini 1 3/4" Underchassis Headers Yet another set of underchassis headers is available from Bob Mazzolini Racing. Choices, choices......   This set of tubes is installed on a 383, and as you can see, clearance to the passenger inner well is tight, so be sure to ask about 440 installs before ordering a set for yourself. They appear very close to the B-body design, but fit much better in the little A-body, and they only fit manual steering. Under the driver side, things are tight, but it all fits. Starter clearance is also tight. Again, on the passenger side, everything fits although there isnt much room for anything else. No dings so far.... Here you can see some VERY tight clearances. The dinged tube near the passenger t-bar, I'm told, wasn't needed. After the tube was squared off, the owner found he could've shimmed the motor enough to clear everything. The owner, John Brennan, mentions that of three cars he's had, this was the only car that was close to the idler arm. He found that, apparently, some replacement idler arms have longer attaching stems and the threads may contact the header tube. Of the three sets of headers in three different cars, this was the only clearance issue he's had....seems like a pretty good design to me. Last, but not least, the passenger collector, complete with 3" exhaust. As far as an underchassis, this set seems to be one of the better ones. Clearance is good, and John states they seem to run well up to about 6500rpm on mild (11-1) engines.