I have a 1968 SS convertible with a non original small block 4 speed car. what is the best engine to put in the car?
1. ZZ4 factory 383/425 crate engine with serpentine system
2. a date correct small block with correct components
3. a date correct big block

thanks for your help

whatever achieves your goal it is your car!
IMO the value of #s matching is gone, you can go for original with the date correct block to salvage as much of the value as possible for a #s car, you can put the big block in for the aww factor at car shows and drags and go original or modern, or you can go with the 383 for more modern power and maybe go with the current trend of pro touring (you could also do the pro touring with the big block)

it all depends on what you would like to achieve with your car. go in the direction that is what you want.

If it were me and money wasn't a huge issue, a ZZ572 that looks like a stock L78/L89.

Or a BIG CUBE small block that looks just like an L48.

You get where I'm coming from no doubt.
So, maybe a mix of your options 1 & 2.
I like cubes and horsepower, and I like a stock look too. It's neat and it's deceiving.:D

Remember, w/o your original engine it will NEVER be stock again and I'm in the same boat.

pdq67 and my now '67SS/RS 496" car.

Lsx / T56

Lsx / T56
That's what I would do too. LS2 or LS7.

No i would stay original looking componenonts but change the inside because then you ahve something that looks original but you could have say a 427 small block or a 383 that has all convential components and looks original and is still just the raw power and ease of use.

Anything you change value is lost and since it is already changed and wont be original it doesnt matter.