The distributor can be any year with an aluminum body through 1972, as long as it's a single-point unit.
You'll definitely need to change the throttle cable and its mounting bracket; if you're not using an OEM carb you'll need a throttle-lever adapter as well. If you're sticking with the automatic, you'll need new throttle-pressure (kickdown) linkage as well as the 318 stuff just won't reach. You could modify yours, though it won't be pretty. The later 1-piece kickdown linkage is a lot less troublesome, which is something to consider while shopping for kickdown linkage. Back to the throttle cable, make sure you get the right one; the small-block cable is longer and will likely kink where it comes out of the firewall. Voice of experience: the multi-strand cable
will abrade and fray inside the housing, and your throttle
will stick... most likely when it's wide open. Rather harrowing with a high-powered big-block, I must admit. If you're going to go with a ridiculous high-rise intake like an M1 single-plane, believe it or not you'll want a Slant Six throttle cable... but for the same reasons above, don't put one in it until the intake is in place.
Avoid later AC bracket setups for the gargantuan 100A Leece-Neville alternator; you'll thank me when you have to replace that pricey bastard. Another benefit of going with the standard brackets is that the Nipple Density (Nippondenso) high-amp alternators from the early '90s trucks are a drop-in replacement. However, a couple of cautions if you make that upgrade: you will definitely want to upgrade the main power feed from the alternator to the battery with 8-gauge or larger wire, and
forget about your in-dash ammeter. The ammeter is only designed for 40A. Wire it directly to the starter relay and from there to the battery. In the immortal words of Phil Hartman's Frankenstein on Saturday Night Live, "Fire
BAD!"
Very important: make sure the bracketry and pulleys you get is the same year range as the water-pump housing you've got, and check your radiator as well. In 1973, it all changed and the water-pump inlet/lower radiator outlet moved to the passenger's side. If you plan to use the original radiator from the LA engine, you'll want to go with the '73 and newer setup--pulleys and all. You won't like me much (not that you did to start with) when I tell you on my last scrap run, an entire '73-style pump-housing setup with the brackets, pulleys, and bolts still attached got turned into tomorrow's Toyota.
On the engine harness, the only thing you need to do is lengthen the primary coil wiring unless you go with the Itchypussy-style (Mitsubishi/ND) alternator. If you had factory electronic ignition, you'd also have to lengthen the distributor wires. Every other wire in the bay will work with the 400, right down to the sender wires. Unless your harness is missing or in really-bad shape, I'd suggest you just cut and splice the coil wires (solder and heat-shrink tubing, obviously). Yes, it's really that simple.
The last time I checked (and I'll be honest, it was a long time ago) the bracketry was being reproduced and the throttle cable was still available new. Bouchillon makes very-good conversion throttle-pressure cables (to replace the linkage), I'm told, but I've never dealt with one personally.
DO NOT drive the car without some kind of throttle-pressure linkage/cable, or your trans will fail in very short order... like, minutes.
