Comments:
1) Timing belt - yes - use Gates not pricey OEM
2) Idlers - yes although probably not "really" needed if solid but a good idea anyway
3) Accessory Belt - yes also Gates
4) Intercooler Hoses (OEMs are weeping) - Samcos
5) OEM Thermostat - don't bother unless temp gauge is reading low. If temp gauge is ok the tstat is easy enough to replace by simply pulling a few coolant hoses and removal of 4 bolts (use wooble 1/4" 6"+ extension drive and 1/4" drive rachet and socket, 10mm IIRC same as for other 3 bolts, to get to invisible lower rear bolt)
6) Fan (Still up in the air between nylon w/ clutch or straight race fan (not a flex fan)) - not sure what you mean by race fan. Flex fan is great but a bit noisey in town between 1500-2000 rpm; cannot really hear it on hwy. Cheapest route is to just install the Hayden fan clutch and keep the metal OEM fan; Hayden engages earlier that OEM clutch which is good and the OEM metal fan moves plenty of air although nylon may move a bit more
7) Drill and tap for a boost gauge. Love to know where you plan to put it - PM or email me please

Clean Clean Clean (darn EGR) - the EGR can be cleaned, see my post at
viewtopic.php?f=5&t=71911 but you might want to check with Keith at GDE. With your tune you may be able to pull the entire EGR assembly and discard; plugging both ends of the EGR pressure lines and rerouting coolant lines of course.
Whatever you do with your fan be sure to do a fan shroud mod, PM/email me if need be, to improve future access.
Alternator decoupler - no particular proactive need, same as tstat. If the serpentine belt tensioner is not bouncing at idle then decoupler is ok. Quality decoupler (not cheap die in 10k junk) runs about $90 while a lifetime warranty alternator from line Autozone can often be obtained for about $150, with good decoupler. Latter may be best long term bet.
Water pump - as with idlers a good idea given that you are already in there. Check Sir Sams neat easy replacement trick of only doing front 1/2 where all the moving parts are
ARP Studs - ??? I don't see where the issue of what ARP studs to use at what torque has been settled or that there is a source for head gaskets (remember they come in 3 thicknesses and you need the right one for your block/head combo) separate from the OEM kit that includes torque to yeald head bolts.
Valve train inspection. - absolutely do lifter/rocker inspection.