I agree that when they were still made/sold by Chrysler via Direct Connection/Mopar Performance, they were completely OEM in quality and performance. In many cases, they were still using "distributors" in cars, so not hard to built them. As things progressed, they were licensed to be built by "somebody else", but to the orig Chrysler specs and quality. It seems that this was initially true, but I suspect that the OEMs aren't policing these things like they were. OEMs are typically more focused on "current and the future" rather than backward.
Proform got their start in the USA (from what I remember) selling "bling" under hood items. Inexpensive (i.e., more affordable) items that appealed to people who wanted such. Sold at auto supplies, usually. Later, they began selling licensed GM chrome things. Next thing I knew, they were selling other OEM-licensed things for other companies. The bulk of it "off-shore" made. Nothing wrong with "off-shore" per se as along as the quality and durability is there, BUT the OEM standards seemed to disappear, by observation.
Used to be that that MP Electronic Ignition Kit plus an earlier model carburetor were all that was needed. By that time, there were usually only one or two part numbers of reman TQuads that anybody carried, covering a broad number of model years and engine shopsizes. Nothing specific to a 440, 400, 360, or 318 . . . more "one size fits all" in nature. I was always a bit suspect of getting any good performance from them, but they probably worked decently well anyway.
In current times, getting OEM-based kits from
@halifaxhops or Rick Ehrenberger's eBay store can be the best ways to do that deal. The orig MP kit was great in that it had all of the factory harnesses to hook things up, with minimal invasion into the vehicle wiring harness. I suspect
@halifaxhops and Rick have similar kits now.
As to the replacement carburetor? The visual favorite would be the Holley Street Demon with the phenolic float bowl. That carb is a Holley clone of the orig TQuad with a few exceptions. Of course, it had the GM and Ford oriented throttle hookup, which will need the adapter to use on Chrysler applications. It will bolt to both square bore and spreadbore manifold flanges, with the secondary throttle plate resembling the old Holley 3bbl carb from the late 1960s. In some part numbers, it can have an electric choke.
Of course, the ultimate replacement would be a new self-learning EFI system which can also control spark timing. For which the OEM Lean Burn distributor might work with it, as just a "distributor" rather than having the spark advance calibrations in it? Although more expeensive, that would update the air/fuel delivery to a currently, perfectly modern system, just as the orig Lean Burn was when it was introduced. Of course, by the time you buy the kit, modify the fuel tank or get a specific EFI model (IF available for those cars), it can be past about $4K, which might be close to what the whole car might be worth. Making the carb/ignition changes more financially viable for most people, IF done correctly.
In prior times, when the LB system had issues, some people went to the auto supply and bought a generic reman distributor, made some wiring adjustments, and "called it a day". Unfortunately, such things usually resulted in the car being sold for a fraction of its prior worth, which meant that the later owners usually trashed formerly great cars as a result. Get the KIT!
A side issue was that by the time the middle 1980s happened and the systems started to have issues, few people at the shops understood the system and made poor repair choices, not knowing what they were doing. We got an Aspen wagon in on trade as it was running poorly and the owners were tired of dealing with it. I had a Chilton book which told how to repair the system with a volt ohm meter rather than Chrysler's "Box" pass/fail item. Our used car tech used that book (knowing that the system was controlled by "voltage and resistance") and got it running pretty good with few parts. And it went to the used car auction.
The bad thing is that to do the system replacement "right" costs about the same as hacking something else onto the car (i.e., "wrong"). Might as well spend your money correctly for the best results . . . for yourself AND the CAR.
Take care,
CBODY67