bcbennett,
The fumes can come from almost anywhere. From the carbs to the tank, and in between. The smell is not good, but the fact that gas is leaking somewhere is definitely not good. You should try to find the source and correct it. Also, it doesn't take much gas -- a tablespoon is enough -- to put out odors you can smell for some distance in a closed garage.
If you don't actually see fuel leaking in the carb area, take a blue paper towel (you can get them at most auto stores) and rub it under each carb, under each float chamber, under each air cleaner, and along fuel lines. If there is a leak, it will show up on the blue paper towel. Leaking carbs and leaking float chambers (the connecting tubes) are primary culprits. Once you find the location of the leak(s), you need to repair it, as you definitely don't want gas leaking onto your manfold, etc.
Look under your gas tank and, if there is a plug there, check it out. The gasket there deteriorates and allows gas to escape. Usually, in that case, there will be some gas on the floor under the plug. If so, drain the tank, take the plug out (carefully), and install a new gasket. I would even recommend a new plug while you are at it. Sometimes the threads on the old plug are shot and a new plug will solve that. You can even wrap it with gas-resistant teflon tape (from auto stores.... not plumbing supplies), and that may help.
As for those burnt oil fumes from oil leaking on the manifold or exhaust pipes, that is normal for these old cars. But there is something you can do to minimize it. First, unless your valve cover is leaking (easily fixed), you probably don't have any oil leaking on the manifold (although you could have gas leaking on it). Most often the smell comes from oil leaking on the exhaust pipes. Other than crawling under your car and cleaning the oil off (like cleaning grease from old kitchen stoves, but worse) from time to time -- which really doesn't do much -- you could try what I did. Auto stores sell sheets of metal that you can wrap around exhaust system components that need temporary repair. I wrapped these sheets around the exhaust pipes where oil has been dripping on my exhaust pipes, held in place with standard metal straps (clamps?). The oil still bakes on the surface of these sheets, but the heat is a little less and the baking is a little less and the smell is considerably less. -- Works, unless, of course, the you like the smell of these old cars.
Be sure to have an exhaust fan going in your garage at all times. Fumes occur naturally, even if you don't have a significant leak. In addition, the fan can help cut down on the damage that moisture and condensation causes (perhaps not a problem in West Texas!).
And, finally, make sure you have a battery cut-off switch on the car, especially if your garage is attached to your house. You don't want to have a fire.
Others with much (much) more knowledge of these things can give you more advice, but this is my two cents worth.