1) Where do I get the kit and what carb would I need to get to match up with it.
Rock Auto lists several carburetor kits for the 2.6:
http://www.rockauto.com/2) What are the most important (maybe even in order, most critical down) things that the 2.6's need done to keep running great?
Timing chain needs to be changed when guides become worn. Remove passenger’s side plastic splash shield from wheel well to expose a small inspection & guide tightening cover on timing chain cover a few inches long held in place by two bolts.
Also you will need to replace water pump pulley seal at end of cam shaft.
Last winter I replaced the timing and balance shaft chain with a kit from Rock Auto that had all new cogs, guides, seals, gaskets, and chains. I posted details about the project, and pitfalls here:
viewtopic.php?f=67&t=6101 Years ago we had a new ‘81 Plymouth Reliant wagon equipped with a 2.6, and it over heated once and cracked the head and K frame at around 40,000 miles; it got traded for an 1986 Lancer. Keep coolant fresh, and shut it down immediately if the engine light comes on, and tow it home; one may get lucky and not crack the head. There may be head gasket problems with these engines due to service department not retorqueing head before car was delivered to first owner; this just a hunch.
I have a 1982 LeBaron Mark Cross Convertible that is original never restored, just mechanically maintained that I ordered in January of 1982. The engine is gutless, but very smooth and quiet once up to speed unlike the noisy 2.2 tractor engine.
By the way I had a head gasket let go on a 1986 turbo Dodge Lancer, and another time slush dripped through hood vent and derailed the timing belt, dealer retro fit a factory recall diverter; it never happened again.
Conquest came with intercooled turbo 2.6 in 1984, its controls are crude, and can experience problems. Dropping one of those engines into a K Car would require a lot of retro fitting, fuel system mods to accommodate EFI, as well as wiring harness changes.
Rock Auto has a boat load of parts for the early K Cars at great prices.
My 1982 Mark Cross Convertible, 72000 mi, unrestored: