wd timing or gas tractor engine

Interesting. We put smaller jets in the carb on our race motors at higher altitudes but left the timing the same.

Maybe and maybe not. Some engines may benefit, others not so much.  Take a WD tractor with 5.5 to 1 compression ratio at 100 psi which is timed at 30 degrees BTDC. I doubt that increasing the timing from 30 to 35 would yield much difference on a fairly low performance engine like that. Then, take a 175 gas tractor with 8.25 to 1 compression at 170 psi which needs to be timed at 22 degrees BTDC to keep detonation in check. There might be an advantage there, but the engine will never perform like it would at sea level timed at 22 degrees.  Some of us older guys are wary of advancing timing on the higher compression gas engines because we have experienced the center main bearing "thump" that comes from too much ignition timing. The "thump" ain't a good thing.  Direct injection diesels with turbochargers are much less affected by the altitude. Direct injection diesels that get the timing advanced are at risk of squirting the fuel over the top of the combustion chamber bowl and over time will burn the top of the piston. Again, some engines react differently than others depending on several things. In-direct inject diesels wouldn't be prone to piston burning, but they are lower performance anyway. So to end my thoughts.....maybe or maybe not.

Neither timing NOR mixture will ever bring a naturally-aspirated IC engine's power up to equate what it would get at significantly lower altitudes... they'll simply dial-in the details that best suit the context.  Compression and mixture are both dynamic circumstances, and atmospheric density has a profound effect on BOTH.