Stock valve springs and stock sized valves would be my recommendation.
Cast pistons offer the best combination of features for longevity and price. They also can run much closer clearances,providing better ring seal and quieter operation.
Clevite makes a nice one piece balance shaft bearing ( no parting line groove). The PN is 1805M (1805M and SH-1429 S on the box).
I have run the Fellpro turbo head gasket with good results. Another favorite is the stock gasket from a Dodge dealer for a 2.6 for a Caravan. It's a graphite gasket that holds up very well. My current motor is 10 years old, so I don't know if they still carry the same part.
I did some checking on piston ring types. For the 2.6, Hastings and Sealed Power only make a chrome rings. That's the part the Randy ( AKA Dad) sells and uses on most of his rebuilds ( and what he recommends).
There is a Japanese (NPR) ring PN SWM31039 that has a molly faced compression ring. I have never tried it, but is seems like a decent part. All ring sets use chrome oil rings.
With a bit of basic block prep, either will work just fine. Ring manufacturing has progressed a lot in the past 20 years and getting rings to seat IMHO / experience is a lot less of an issue. That includes engines that I have done simple freshen ups on with a de-glazing hone.
Basically, moly is generally better, chrome works really well and is much easier to source.
That experience includes the following donts:
Don't use gapless rings ( AKA TS).
Run the second ring gap to the wide side. That allows for a better pressure differential across the top ring. Personal testing and research by Ford has proven that this is effective.
Don't use a grooved balance shaft bearings.
Don't try and reto fit your stock cam with roller rockers. I have a lot of data on this.... Short answer is its the wrong approach.
Balance shafts work and make a nice difference in how smooth the motor is. I run them, others seem OK without them. No problems in ten years. If you good oil pressure, the balance shafts will live forever.
The stock style cast aluminum oil pump is the best and any cast iron aftermarket pump is a downgrade.
Read the TSB on the oil pump drive chain. Torque values changed. They may have changed on the head gaskets as well.
Be careful of what pistons you choose. One manf has (used to have) a universal set of pistons that they list for turbo and non turbo. The turbo motor has a stock 7 to 1 CR. The universal pistons are "decked" to allow for milled heads (pretty common on rebuilds). With a lightly cut head you end up with a 6.5 to 1 compression ratio! If memory serves me right, with some combinations of parts, 6 to 1 was possible.
IF you end up with those, the motor will seem a bit doggy, slightly harder to start and you will get some low number like 120 psi when you run a compression test.
Most aftermarket pistons are decked about 1/2 CR point. For a non turbo motor, try and shoot for a minimum CR of 8 to 1.
I have run ACL pistons. Very light, short skirt nice design. They are a bit more prone to slap when cold, overall a nice part. Not sure if they are still available. Sealed power is another good choice, they are typically a hyperutetic alloy.
Get a fresh set of stock head bolts, skip the ARP studs. Use a thread cleaning tap on all the bolt holes.
Crack check the deck of the block. A hard overheat can (often) crack the block around the exhaust bolts holes. That can result in a motor that always loses head gaskets for no obvious reason. The hard overheat is a reason to stick with stock bolts. The stock bolts will yield and reduce the chance of a cracked block, the ARP's will generate a lot more force before they yield.
I run ARP studs on my turbo motor, they do work but stock is fine for almost any build.
A light cut to the deck is cheap insurance that you have a good gasket surface. Also check your cylinder bores for pitting. Motors that have lost a head gasket and then sat, often have badly pitted bores.
Main Bearings:
I have run aluminum bearing and tri metals. Both give good service. The tri-metals a a bit more forgiving to dirt in the motor during assembly. Either works just fine. ACL makes a nice aluminum bearing set.
Its been a while since I have done a 2.6, so I don't have the all the PN's handy. In general; the closer to stock, the better.
Also, make sure your distributor is working correctly. The grease in mechanical advance mechanism hardens and you don't get a smooth mechanical advance. The vacuum diagram seems to hold up, but should be checked.
On my turbo 2.6, the mechanical advance had ovaled out when it had advanced to the cruise RPM position. The motor ran hot, chugged fuel and had poor power.
In short... Before you start your motor, make sure the carb and dist are good (same with the cooling system).
You should be able to source all your parts yourself for not too much money.
