MLB's Field Of Dreams

The MLB's Field Of Dreams replica officially has Ray Kinsella's stamp of approval ... 'cause Kevin Costner visited it this week and GUSHED over the ballpark, calling it "perfect."

Costner -- who played Kinsella in the 1989 classic baseball movie -- got a tour of the Dyersville, Iowa field just before the Yanks and the White Sox play there Thursday night, and his reaction was awesome.

The 66-year-old walked through the bleachers and stepped on the infield grass ... and was astonished, looking around in bewilderment at how the MLB made the fictional field come to life for an actual game.

"Wow," Costner said. "Feels perfect. Every bit of it."

Of course, the endorsement is big for the MLB ...…