A heatercore I'm using in my YY cube is GM 2-471 . It is 9 1/2" x 5 5/8" x 2. The GM 2-250 is a lttle smaller, 8" x 5 5/8" x 2".
I'm fitting in the big one, 2-471. It's for a 1977 Chevrolet Caprice 305 U 8 cylinder with ac. Autozone nr 399078 for $18 ex shipping. It fits with the tanks just between the top and bottom edges of the door. I'll try to make it a side discharge, not through the front. I'll put the whole cube in a coffee table when I'm finished with the case (reel soon now
) At least that is what I though a year ago. The side discharge is so I can build it in shielding the sound of the fans better. I like a perfectly quiet computer...