I'm sure this has been asked a 1000 times. So let me make it 1001. How difficult would it be to build up a standard 289 engine to semi K-code specs? I know that's an open ended question so let me put some parameters around it.
Looks reasonably like a K-code engine from the outside. I.E. no aftermarket heads, carburators, etc.
So far, pretty easy.
Date coding not important.
Using a standard 289 A-code engine that is due for it's first rebuild.
Same block, so no problem.
Solid lifters preferred because I like the sound.
The C3OZ-6250-C 289HP cam is available, so go for it.
No vacuum dizzy would be nice, Motorcraft replacement fine.
These turn up all the time on ebaY.
Use real or reproduction HIPO exhaust
The 289HP repro manifolds are available, and very good quality.
Prefer to use 4100 Autolite carb. Rebuilt to flow 600cfm?
You can't bore out a 1.08 to 1.12, so you'll have to get a replica. Doable.
271 HP at flywheel or better
Too easy. If you port-match the heads to the manifolds, you'll exceed that.
Essentially I'm looking for the look and feel of a K-code that would look period correct with a casual glance. I'm not interested in most horsepower for the dollar nor do I feel necessarily compelled to use real k-code parts due to the expense. Looking for a nice compromise.
If you use upgrade connecting rod bolts, 289HP balancer and hatched weight, "thin" timing set, and get the assembly rebalanced, (which you'll do anyway), as well as the above mods, plus screw-in rocker studs, dual valve springs, big alternator pulley, special fan, and the chrome valve covers and air cleaner, you pretty much have a 289HP.
The only thing short of it at that point is the bigger con rod bolts, and thick main caps, and you've gone all the way.
These engines were more than the sum of the parts, they ran really well, because they had a balanced setup.
Car would be a 65 GT coupe.
Since real K-codes came with the 9" rear-end, would that need to be upgraded as well?
You will if you intend to beat the tar out of it. Or, if you get a Currie 4-pinion 8" Traction-Lok, your 8" will be stronger than many stock 9" rears.
I realize that more modern and aftermarket parts would make more horsepower and do it more cheaply, but that's not what I'm looking for. I like the idea of "old school" technology and want a vintage look and sound. Adjusting solid lifters doesn't bother me and the car isn't a daily driver anyways.
The 289HP duals with twin mufflers and twin resonators sound great, and are readily available. I drove my 289HP daily for years, and got to where I could adjust the lifters in less than an hour.
Here's a Mustang Monthly article where they did essentially the same thing with a modern block.
1965 Hi-Po Engine vs. Shelby 289 Short-Block - Mustang Monthly
Not sure I'd use that as a guide. They used the wrong valves.
I'm not using the stock rockers in my 289HP, though, the uniball fulcrum style was a problem, even Ford dropped them fairly quickly. This article explains what I did-
289 High Performance Valve Train Upgrade
I kind of like what they did but want to do it with a standard 289 block. The water pump and dizzy are ugly though in my mind.
The 289 2V and 289HP had the same block. Really. The 289 2V and 289HP water pumps were externally identical. You can use the regular water pump and you'll never know.
Dunno why you would think the pump and distributor are ugly-