I have a basement block wall with an odd-sized opening (37"x79.5"). I tried buying a custom steel door, but they wouldn't make it that height (77"). So I was thinking I could buy a solid door and cut it to size. The only problem is I'm not sure how to attach the jamb to the block, and I am not sure if the two materials should even be used together. Any thoughts would be appreciated.

Yes, you can use a wood door. A steel door would be better for security and longevity but if you can't, you can't.

You can probably take a steel door, cut off the bottom and then close the bottom by inserting a filler strip of pressure treated wood and silicone. Only problem with doing that is you would probably want to run a couple screws in from each side which might be slightly unsightly.

You should be able to purchase a 32" door, either wood or steel, and fill the hole with treated wood. You can enlarge the opening, at least width wise by scoring and then chipping out block. Block is fairly easy to chip away.

I think I would install a pressure treated wooden frame of the proper size, bolted to the block with lag bolts and lead anchors or molly bolts. Then install the door and frame.

What is the top of the opening, block, steel lentil or wooden plate?