I found a transmission shop in Manchester, TN. Many praises to Banner Automotive. They were quick with repairs.
Now that all is finallly fixed, the source of the problem and noise: One of the internal bearings failed. After that the the gears on the input shaft and the cluster gear were torn up. After both of those being replaced, new seals, syncros... , plus labor; ouch!! And a new SBC clutch and needle bearing.
The transmission shop said the transmission was low on oil, not empty but still low. A lot can be said for checking fluids regularly.