I only did one 029 to 390 conversion, so I can say I've done one. I've turned other dead ones away since then.
Rather work on a 044/440, 046/460 or 066/660 anytime. Getting to know those models fairly well, and they are not so tricky! I also like that you can adjust your squish.
Muff mods and timing advances are also much easier!
If I'm not mistaken, the HD-11 has the richest jetting, but they seem to be NLA. They originally came on heated handle 044s. I believe the HD-50 has totally different jetting (the 461 carb), but only my Ported 460 seemed to really like it.
Conversely my Hybrid really liked the HD-11, but most other saws did not really seem to care!
I have HD-16 carbs off 460s followed by A, B or C. I have no idea what the differences are, but if anyone knows, please share.[/QUOTE. I would much rather work on any pro style saw . No comparison on which is easier