Pet peeves: squeaks

[Mike_The_Grad]

We all got 'em. (Pet peeves I mean.) Mine are squeaks and leaks.
This post is directed at those annoying sounds that either come and go, are consistent, or occur only under certain conditions.

I've had one that I may have become tone deaf to, or at least I tune it out. It only happens while the vehicle is in motion. Driving down any street, new or potholed, below 45 m.p.h. it doesn't matter if it's a dip in the road, coming to a stop, accelerating, driving straight, or making a turn. During or for about a day after it rains, my truck won't make a peep. But the second it happens again it's the only thing I can think of.

Now I know there's only about a million things that could cause this. But maybe a little information can help narrow it down. Starting at the front: all bolts on the front end sheet metal are tight, there are no obvious signs of rubbing on any body panels or joints, the front suspension of my 1972 c10 LWB with factory overload rear leafs is pretty well lubed up but I will do my semi-annual chassis lubing today just to make sure, my core support bushings are about 2 years old and not dry or cracked, I recently installed a front sway bar with polygraphite bushings (the squeak occurred before this installation.), I have new front disc rotors and wheel bearings (about 6 months old.I will be checking them today as well.), original calipers with the bolts and slide bushings lubed (again I will be checking these today as well), the cab mounts have seen better days but they are still there and not squished out, my driveshaft has brand new u joints and center support bearing (literally about a week old.), the rear drum brakes were overhauled the same week along with new axle bearings and seals.
The rear leaf suspension is old and rusty. Here is where I'm thinking is most likely the origin of my squeak.
Is there a way to lube up the rear suspension? If so, where and what to use?
Also any thoughts or opinions are appreciated
(Windows have new felts and guides, regulators and internals are all lubed, new door panel retainers, new handles and cranks. Happens with Windows up or down. Happens at night and in the day time. I highly doubt the squeak is mechanically related to the engine, I have new motor mounts and trans mount, new belts that are properly tensioned.)
Oh, and yes I do turn my stereo up just to relieve the mental torment.
Thanks in advance.