The text mentions two things that Johnny admires about Dally in chapter 5. The first is that Dally can swear and cuss really well.
He took a drag on his cigarette and cussed it goodnaturedly for not being a Kool. Johnny listened in admiration. "You sure can cuss good, Dally."
That's kind of an odd thing to admire about somebody, but then again the swearing is just part of Dally's entire persona. That's what Johnny is truly in awe of.
Earlier in the chapter, Ponyboy and Johnny are trying to kill time while hiding out from the police. Ponyboy reads aloud so that Johnny can experience Gone with the Wind as well. That is most definitely an odd literature choice for a pair of hardened gang members, but Johnny makes the comment that he likes the way that the Southern gentlemen act. He says that they remind him of Dally.
"I bet they were cool ol' guys," he said, his eyes glowing, after I had read the part about them riding into sure death because they were gallant. "They remind me of Dally."
Ponyboy questions what Johnny means, because Dally is the farthest thing from a gentleman. Johnny elaborates a bit in the next paragraph.
"Yeah... in the manners bit, and the charm, too, I guess," Johnny said slowly, "but one night I saw Dally gettin' picked up by the fuzz, and he kept real cool and calm the whole time. They was gettin' him for breakin' out the windows in the school building, and it was Two-Bit who did that. And Dally knew it. But he just took the sentence without battin' an eye or even denyin' it. That's gallant."
Johnny deeply admires Dally's gallantry. His cool and calm demeanor makes Dally seem practically unflappable.
In this chapter, Dallas Winston (Dally) comes up to the old church to see Johnny and Ponyboy. He had told them to go up to the church to hide after the two of them killed the Soc (Bob) who had hurt Johnny so badly in the past.
Dally finds Johnny and Pony and wakes them up. While Pony is reading the letter Dally brought, Dally smokes a cigarette that Pony gives him. Dally curses the cigarette because it is the wrong brand.
When he does that, Johnny admires how well he can curse.