Berg dip stick thermometer: Yeah, it's nice, but all it does is make your oil pressure light come on at 225 degrees or so - it doesn't actually tell you what the temperature really is. For that, get a decent candy thermometer with an 8"+ long probe, instant read is a bonus, and use that to calibrate your dash gauge.
welded and balanced fan - Absolutely
serpentine fan belt (Greg says no) No. Just no. Even if Stan has one, no.
Thicker sway bars - Yes, but if you have a swing arm rear end you'll need a camber compensator instead. 3/8" up front is nice. 3/4" up front is kinda stiff.
transmission brace - If this is a mid-brace, then yes. I have one and it helps to stiffen things up back there nicely. Add a Kafer Truss Bar and it gets even stiffer. Don't forget to upgrade the transaxle front mount to a Rhino version.
3 or 4 point seat belts - Sure. Self retracting is a bonus.
twin plug heads - Only if you have Stan's budget. Remember that this is the tip of a very, VERY large cash flow iceberg.
case breather systems (Vintage Speed) - Berg has a really good one, too, that looks more like a 912 breather.
upgraded gas pedal (Vintage Speed) - Meh.
2 post lift - Yes, if you have the room
New garage - Yes, if you have the room - Does the budget for this come out of the car budget? Mine did. 
No specific order - Well, your cash flow budget might have something to say about this.