Thank you guys. As Derek with Vice Grip Garage would say "Well I'll be dipped". And CBODY67 is on the right track! Here's what happened just in the hour since I posted this.........
After I posted this topic, I went on youtube to see what videos were available to address the removal of the exhaust manifold bolts (or nuts in my case, as CBARGE correctly points out). I watched a couple of good videos, very informative. I then went out to the compound to have a look at how difficult it would be to access the nuts. I got out the shop light and the mirror and started looking around. When I got to looking at the very last bolt, it caught my eye, as it looked....well....loose! And this is the flange that is leaking, closest to the firewall on the driver side. I grabbed a socket and extender and sure enough, as impossible as it seems, the last nut was finger loose. It just seems impossible that a rusty manifold nut could back itself out that far, but damn if it wasn't loose. SO, I tightened down that nut, and it's neighbor (which was also slightly loose), and voila!, the exhaust leak is fixed! I'm not big on conspiracy theories, but.....
Now I am wondering if it isn't sabotage. I had a shop do some work on the exhaust system a few months back. The manifold leak started around that time, but it would seal up when the engine got warm, so with everything else going on, I figured I wait to take it back there, since there was a 2-year warranty on their work. THEN, there appeared to be a loose hanger, and I could hear a pipe banging on the floor under certain conditions. So I did take the car back, the guys put it up on the lift, then informed me he'd fix the issues, but now there was a gas leak at the tank, so he'd need to drop the tank and repair the leaking fuel hose before he could do any exhaust work. I didn't doubt that, the car is 53 years old, right? But I didn't have time that day, so I made an appointment for the next week. MEANWHILE, over the weekend (last weekend) I jacked the car up, slid under, and observed that there was in fact NO GAS LEAK, and nor was there any evidence of one ever. AND, if there were any leaking fuel hose, it would not require that the tank be dropped. I knew if the tank were dropped, the strap removal probably would start a leak, and then he'd be trying to sell me a replacement tank and labor for $500.
SO, (sorry for the long story), I took the car back at the appointed time, they got it on the lift, and before I could tell the guy I was wise to his gas leak ruse, he calls me into the bay to show me the gas leak! I lost my ****. It was obvious he'd pushed on the rubber fuel line hard enough to cause it to start dripping. I was blind with rage. I told that SOB I knew exactly what he was trying to pull. As he was taking the car off the lift, I informed the guy in the waiting room that these guys were crooks, and I left. I fixed his leak that same day with a 6" piece of fuel hose and 2 clamps, done deal.
NOW, with the most accessible nut on the manifold finger-loose, I can't help wonder if those jokers didn't back that nut off, assuming I'd return for another $500 clip job. And this isn't the first time I've had a muffler shop come into the waiting room and tell me I had a gas leak. The first time about 10 years ago on another classic car. Once under that car, I saw it was a drain plug leaking, so I grabbed his wrench, tightened the plug, wiped the nipple, and told him to keep going.
The moral of the story is..... these muffler guys don't seem to have any morals!! I swear I am going to install a lift at my compound so I don't have to put up with these crooks any more. Thanks again fellas for all your help with these posts, it is most appreciated.
Rich