Particular situation on a new rebuilt block need help!

The crank and damper are not the problem. You can stick the newer or older timing cover/ pulleys/ etc on the front with no issues. Some years have a symmetrical pattern for the pulley bolt holes, and some do not. It is common to either leave the odd bolt out or oblong the hole in the pulley

The timing mark is easy to deal with. Use a piston stop. In fact this would be a great time to degree your balancer.

https://www.forabodiesonly.com/mopar/threads/piston-stop-advice.241628/
Remove battery ground for safety, and get a socket for the balancer bolt. Use a probe "roughly" to make sure the no1 piston is down far enough. Install the stop device and wrench the engine around carefully until rotation is stopped by the device. Make a temp mark under TDC on your (new) pointer. Rotate engine backwards again until it stops. Make a second mark under TDC.

You will have two marks some distance apart. TDC is halfway between.

To degree, use a small flex tape (lying under car is sometimes actually easier) and measure carefully around damper rim. Figure out how many degrees per inch, and then carefully measure off that amount and mark something like 20 or 40 degrees. RE RE check this CAREFULLY

Now, using dividers directly on the wheel, you can dived this 20 or 40 and extend or divide from there. Divide again to mark 10 degree points, etc. Use a small square and scribe, then a small file, etc to mark.

If you have numerical stamps you can mark, say, 20 and 40 and eyeball from there