71 LA 340 timings moved!! how?? looking for help

The most important timing is power-timing. 50* is about 16 to 18 too much; you HAVE to back it up, no maybes, if you value that engine. Let the idle timing be whatever, but get the power timing down to 32/34 maximum for now.
You will need a dial-back timing lite, OR a timing tape, OR you will have to calibrate your balancer.
Then you just pull the timing out until no matter how hi you rev it,the timing no longer increases to past 32/34.Then let the idle timing be whatever.Now maybe you can run pump gas which I heard in your country is pretty low-octane.

And then once the power-timing is reset, you can re-connect the Vcan.
And then we can talk about the hesitations,bogs, or PT pinging,that might have developed.