Edited on 2015-01-27 12:11:51
I'm no engine mechanic but I have rebuilt the 4 carbs on my '72 with great success. Long but fun and relatively easy project. I also got to clean up a lot of grime you can't normally reach.
This sounds like a fuel delivery problem. Is the fuel pump working properly? I changed mine to a new, little, shiny modern pump and gained a ton of performance. My next project is to get the old pump working properly and re-install it..
I am assuming that you are using new gasoline and changed the filter.
On a side note, if you want to give that "bad old" engine to someone, I'll take it.
PS - On mine, the vacuum hoses were all original. They went to the right places and all that. Problem was they were hard and leaked like crazy. Some would break when you touched them (no joke). I replaced every inch and fixed several problems including rough idle, smoky warm up and more.
Just a thought.
I've been where you are and it is frustrating. Welcome to XKE land.
It is also worth the effort.