Clints horse at the end of the masterpiece

[Novecento]

Frayling has said that by the time of GBU, Leone was already thinking about making OUATIA.
Perhaps the mausoleum is a bit of unintentional foreshadowing 

Perhaps, but that's quite a stretch; the mausoleum is a key plot point in OUATIA. Nonetheless, you make an interesting connection.

[drinkanddestroy]

I am not making a connection; I am just making a joke  

The whole 1968 part of OUATIA was not in The Hoods. Leone certainly was not thinking about a mausoleum in OUATIA during filming of GBU  

[Novecento]

phew 

[uncknown]

better question -- how could Angel Eyes sneak up on Blondie & Tuco in a huge open field where there are nothing but graves as far as the eye can see?

In the uncut version he takes his boots off