Welcome mate to the forum.
Good to here your making a comeback afetr a long break, there's been a lot of riders signing up recently who've been off the scene for the past 5-10 years!
If your after a stem then your best having a look on tartybikes website, I've done the same as you after riding stock years ago I've built myself a mod up as well and I use a trialtech race forged one which gives a fair amount of length and rise.
As for a freewheel you can't go wrong with either of the tensiles or if you can afford it the Echo SL 108 would be ideal. Complete spares can be bought for the tensiles whereas the Echo is renowned for being quite indestructable, I've got both so can recommend either depending on your budget.
As for hubs I built my mod on a relatively low budget for new stuff and I've found the Onza sealed hubs to be just fine for the job at hand, if not you won't go wrong with some trialtechs but again its down to your budget.
Hope that helps!