This is the engine in my 71 429 CJ Mach. Over the years, many subtle...and not so subtle changes have taken place, and not always intentionally.
My car was stolen twice over the years, and thankfully recovered each time. The second time it came back with the entire ram-air system, including the air cleaner assembly missing, among other things.
I pieced the system back together as I found the correct stuff, but the "J"-code 429 Ram-Air air-cleaner is a hard beast to locate. And if you do find one, they are exorbitantly expensive.
So...I pieced together and cobbled-up a replica as best as my limited budget allowed me to at the time. I combind a couple of junkyard air-cleaner parts with a new gasket and some fresh blue paint, and while it certainly does not look original to even the most casually-astute Mustang aficianado, it serves the purpose and presents reasonably well when I open the hood. Good enough for me.
In one of my many accidents, the fan shroud met its demise, and the correct 429 shrouds are also difficult to locate...a shroud from a 400-equipped "Country Squire" wagon fits exactly perfectly, and only the embossed "CAUTION FAN" gives it away as non-original.
My valve covers rusted away to the point of replacement, and I used the custom "429 Cobra" replacement covers. Definitely not original, but I like the looks of them.
When I rebuilt the engine (at 325,000 trouble-free miles!), I installed some worked heads off of a 73 460 PI engine along with an Edelbrock "Performer" intake. This combo is far superior to the stock CJ heads and manifold. I have those parts stored away for posterity!
I have always been tempted to grind down the "Edelbrock" logos and such on the manifold and paint it Ford-blue to further the illusion...but I never got around to it.
I kept the stock exhaust manifolds, but had them "extrude honed" to increase thier flow and it made a surprising improvement. A true 100% invisible performance modification.
I installed a Ford "DuraSpark II" ignition system from a wrecked '77 460-equipped Econoline, and that made a huge difference. This was well before "Pertronix" had arrived on the scene. I blueprinted the distributor myself (a surprisingly easy and very effective mod to do yourself) and then kit-bashed a few parts together to give it the look of the original ditributor.
I simulated some now-unnecesary vacuum-hoses and heater stove-pipes to give it a more stock look, but they are not functional.
painted the new coil top yellow, painted a new electronic voltage regulataor blue (a vast improvement over the old stock points-fired VR), added a couple of appropriate repro decals to each of them and they look pretty much the part of original equipment.
I added a repro "Motorcraft" battery top, and it looks great too...fools a lot of people. Although it is technically incorrect as "Autolite" was the name of the Ford parts division in 71, but there are no repro "Autolite" battery tops, so...this one does nicely.
Added a hidden recovery bottle to the cooling system with a recovery-style cap, and that help also.
The idea was to always keep the car looking as close to "original" (or maybe "simulated original") as was reasonably possible and still have a trouble-free driver.
There are many, many details on my car..some small, others quite obvious that are "incorrect" as far as strict originality goes. It is not a show car, and never will be, so my intention is to rate functionality and reasonable expense as the priority and an appearance of originality slightly below that.